Entry - #162400 - NEUROPATHY, HEREDITARY SENSORY AND AUTONOMIC, TYPE IA; HSAN1A - OMIM
# 162400

NEUROPATHY, HEREDITARY SENSORY AND AUTONOMIC, TYPE IA; HSAN1A


Alternative titles; symbols

HSAN IA
HSAN1
NEUROPATHY, HEREDITARY SENSORY, TYPE IA; HSN1A
HSN IA
NEUROPATHY, HEREDITARY SENSORY RADICULAR, AUTOSOMAL DOMINANT, TYPE 1A


Phenotype-Gene Relationships

Location Phenotype Phenotype
MIM number
Inheritance Phenotype
mapping key
Gene/Locus Gene/Locus
MIM number
9q22.31 Neuropathy, hereditary sensory and autonomic, type IA 162400 AD 3 SPTLC1 605712
Clinical Synopsis
 
Phenotypic Series
 

INHERITANCE
- Autosomal dominant
HEAD & NECK
Ears
- Deafness, sensorineural (reported in 1 family)
Eyes
- Macular telangiectasia type 2 (in some patients)
- Cataracts (in some patients)
SKELETAL
- Osteomyelitis
Hands
- Osteomyelitis or necrosis, distal, due to sensory neuropathy
- Autoamputation
Feet
- Pes cavus
- Osteomyelitis or necrosis, distal, due to sensory neuropathy
- Autoamputation
SKIN, NAILS, & HAIR
Skin
- Ulcers, distal, painless, due to sensory neuropathy
NEUROLOGIC
Peripheral Nervous System
- Distal sensory loss of all modalities (pain, temperature, touch, vibration)
- Taste is spared
- Sharp, 'lightning'-like pain
- Distal limb muscular atrophy due to peripheral neuropathy
- Distal limb muscular weakness due to peripheral neuropathy
- Distal hyporeflexia
- Distal areflexia
- Lower limbs more severely affected than upper limbs
- Autonomic involvement is variable
- Motor involvement is variable
- Axonal neuropathy, chronic, seen on EMG
- Decreased sensory nerve action potentials
- Dorsal spinal columns are diminished in size
- Dorsal nerve roots and ganglia cells show degenerative changes
- Distal nerve biopsy shows decreased numbers of small myelinated and unmyelinated fibers
- Loss of large myelinated fibers
MISCELLANEOUS
- Onset usually in the second to fourth decades of life
- Some patients with childhood onset and a more severe phenotype have been reported
MOLECULAR BASIS
- Caused by mutation in the long-chain base subunit 1 of the serine palmitoyltransferase gene (SPTLC1, 605712.0001)

TEXT

A number sign (#) is used with this entry because hereditary sensory neuropathy type IA (HSAN1A) is caused by heterozygous mutation in the SPTLC1 gene (605712) on chromosome 9q22.


Description

Hereditary sensory and autonomic neuropathy type IA (HSAN1A) is an autosomal dominant neurologic disorder characterized by sensory neuropathy with variable autonomic and motor involvement. Most patients have adult onset of slowly progressive distal sensory impairment manifest as numbness, tingling, or pain, as well as distal muscle atrophy. Complications include ulceration and osteomyelitis. Some patients may have a more severe phenotype with onset in childhood. Electrophysiologic studies show a predominantly axonal neuropathy with some demyelinating features. Some patients may have evidence of central nervous system involvement, including macular telangiectasia type 2. Affected individuals have increased levels of plasma 1-deoxysphingolipids (1-deoxySLs), which are thought to be neurotoxic (summary by Rotthier et al., 2010 and Gantner et al., 2019). Oral supplementation with serine decreases 1-deoxySL and may offer some clinical benefits (Fridman et al., 2019).

Genetic Heterogeneity of Hereditary Sensory and Autonomic Neuropathy

See also HSAN1C (613640), caused by mutation in the SPTLC2 gene (605713) on 14q24; HSN1D (613708), caused by mutation in the ATL1 gene (606439) on 14q22; HSN1E (614116), caused by mutation in the DNMT1 gene (126375) on 19p13; HSN1F (615632), caused by mutation in the ATL3 gene (609369) on 11q13; HSAN2A (201300), caused by mutation in the HSN2 isoform of the WNK1 gene (605232) on 12p13; HSAN2B (613115), caused by mutation in the FAM134B gene (613114) on 5p15; HSN2C (614213), caused by mutation in the KIF1A gene (601255) on 2q37; HSAN2D (see 243000), caused by mutation in the SCN9A gene (603415) on 2q24; HSAN3 (223900), caused by mutation in the ELP1 gene (603722) on 9q31; HSAN4 (256800), caused by mutation in the NTRK1 gene (191315) on 1q23; HSAN5 (608654), caused by mutation in the NGF gene (162030) on 1p13; HSAN6 (614653), caused by mutation in the DST gene (113810) on 6p12; HSAN7 (615548), caused by mutation in the SCN11A gene (604385) on 3p22; and HSAN8 (616488), caused by mutation in the PRDM12 gene (616458) on chromosome 9q34.

Adult-onset HSAN with anosmia (608720) may be another distinct form of HSAN, and HSAN1B (608088) with cough and gastroesophageal reflux maps to chromosome 3p24-p22.


Clinical Features

Hicks (1922) described an English family in which 10 members suffered from perforating ulcers of the feet, shooting pains, and deafness. Age of onset ranged from 15 to 36 years. Presentation was usually with a corn on a big toe followed by a painless ulcer with bony debris. Patients later experienced shooting pains similar to the lightning pains of tabes dorsalis and developed bilateral deafness progressing to total deafness over several years. Neurologic examination showed disappearance of ankle and knee jerks and absence of an extensor plantar response. There was loss of pain, touch, heat, and cold sensation over the feet, but sensation of the arms remained normal. Cranial nerves were normal, with the exception of the auditory nerve, pupils reacted normally, and there was no nystagmus. Hicks (1922) noted that although hereditary perforating ulcers of the feet had been reported in patients in the past, there had been no previous mention of accompanying deafness or shooting pains. Denny-Brown (1951) reported the clinical and autopsy findings of a 53-year-old woman who was a member of the family reported by Hicks (1922). When she was 22 years of age, an ulcer formed on her right great toe, requiring a year to heal. She subsequently suffered from recurrent ulceration, each episode lasting 6 to 9 months and sometimes extending to bone. In her early twenties, she first noticed shooting pains in her legs, sometimes in her arms. Deafness began at the age of 40 years and progressed to almost total deafness by 53 years of age. Neurologic examination at 53 years of age showed loss of all sensation in the lower legs, with loss of pain and temperature sensation in the thighs and hands. Autopsy showed a small brain and marked loss of ganglion cells in the sacral and lumbar dorsal root ganglia. Remaining ganglion cells showed proliferation of subcapsular dendrites and hyaline bodies, possibly representing an amyloid mass around capillaries. There were less severe changes in C-8 and T-1 ganglia. The affected families reported by Ervin and Sternbach (1960) and Silverman and Gilden (1959) appeared to show autosomal dominant inheritance. Mandell and Smith (1960) observed sensory radicular neuropathy in 3 generations of a family. Clinical features included neuropathic arthropathy, recurrent ulceration of the lower extremities, and signs of radicular sensory deficiency in both the upper and the lower extremities without any motor dysfunction. Dyck et al. (1965) described a family with sensory neuropathy accompanied by peroneal muscular atrophy and pes cavus. Campbell and Hoffman (1964) and DeLeon (1969) also reported cases in which amyotrophy was a feature. Using a cholinesterase technique on skin biopsies from the pad of the great toe of affected persons, Dyck et al. (1965) found normal numbers of Meissner corpuscles in a 14-year-old boy with early signs suggestive of the disorder, but no corpuscles in a 37-year-old man and a 28-year-old woman with well-developed disease.

Dyck et al. (1983) noted that 'burning feet' may be the only manifestation of dominantly inherited sensory neuropathy. The symptoms are ameliorated by cold and aggravated by heat. Restless legs and lancinating pain are other presentations of the disorder, which often resulted in severe distal sensory loss, mutilating acropathy, and neurotrophic arthropathy.

In a detailed clinical study of a patient with HSN1, including audiometric testing, autonomic functions, electromyography, transcranial magnetic stimulation, and brain imaging, Hageman et al. (1992) determined that there were no signs of central nervous system involvement and stated that HSN1 is a disorder of the dorsal root ganglia and peripheral nerves.

Wallace (1968, 1970) studied an extensively affected Australian kindred. In a study of this kindred and 3 other Australian kindreds with HSAN1, Nicholson et al. (1996) found that a typical history included lightning pains, painless skin injuries and ulceration, and signs including distal sensory loss to sharp, hot, and cold sensation, with loss of distal reflexes and distal muscle wasting. Nerve conduction velocities showed an axonal neuropathy, particularly of the lower limbs.

Dubourg et al. (2000) reported a French family with autosomal dominant hereditary sensory neuropathy suggestive of linkage to chromosome 9q. Mean age at onset was 34 years. All patients presented with distal sensory loss and distal muscle weakness of both the upper and lower limbs. Four patients had foot ulcerations, and 3 patients had hyperhidrosis. Motor nerve conduction velocities were normal or mildly decreased, consistent with an axonal neuropathy. Sensory nerve action potentials were either reduced or could not be recorded.

Severe Phenotype

Rotthier et al. (2009) reported a French Gypsy patient with an unusually severe form of HSAN1. The patient had congenital insensitivity to pain with eschar and foot ulceration, pes cavus/equinovarus, vocal cord paralysis, and gastroesophageal reflux. The patient also had severe growth and mental retardation, microcephaly, hypotonia, amyotrophy, and respiratory insufficiency. Nerve conduction studies showed absent sensory and motor responses in the upper and lower limbs. Genetic analysis identified a de novo heterozygous mutation in the SPTLC1 gene (S331F; 605712.0005). The phenotype expanded the clinical spectrum of HSAN1.

Auer-Grumbach et al. (2013) reported that a patient (ER-CIPA-20374) described by Huehne et al. (2008) with a severe form of HSAN1 had the same heterozygous S331F mutation in the SPTLC1 gene as that reported by Rotthier et al. (2009) in a patient with early-onset severe HSAN1A. The patient described by Huehne et al. (2008) and Auer-Grumbach et al. (2013) had onset in early childhood or muscle weakness and hypotrophy in addition to prominent sensory disturbances, bone fractures, and osteomyelitis. The patient developed cataract at age 9 years, complete retinal detachment at age 10, and repetitive corneal ulceration and keratitis with poor wound healing.

In another patient with a severe form of HSAN1, Auer-Grumbach et al. (2013) identified a different de novo heterozygous mutation at the same codon (S331Y; 605712.0007). This patient had onset at age 4 years of unsteady gait, hand tremor, mild sensory disturbances, and a pes cavus foot deformity necessitating triple arthrodesis at age 5. At examination at age 12, there was general muscle hypotrophy and hypotonia with pronounced weakness in the distal muscles of the upper and lower limbs. There were prominent sensory disturbances; these were pronounced in the feet and affected all qualities except for the vibration sense, which remained completely preserved. At the toes, scars from burns due to reduced pain and temperature sensation were evident. There was also hypermobility of the joints, bilateral hand tremor, and fasciculations, most prominent in the tongue. At age 13, she developed bilateral cataracts. Disease progression was rapid and led to severe scoliosis, respiratory problems, and wheelchair dependence at age 14. The patient had prominent growth retardation but normal intellectual development. The level of 1-deoxySL was significantly elevated in the patient's plasma.

Association with Macular Telangiectasia Type 2

Gantner et al. (2019) identified 9 patients, including 8 patients from 2 unrelated families and an additional unrelated patient, with genetically confirmed HSAN1A who also had type 2 macular telangiectasia. All carried the same heterozygous C133Y mutation in the SPTLC1 gene (605712.0001). The proband in the first family presented with bilateral bull's eye maculopathy at 21 years of age. Detailed ophthalmologic examination showed findings diagnostic for macular telangiectasia type 2, including parafoveal telangiectatic retinal vessels, 'right angle' venules, retinal opacification, pigment clumping, low levels of macular carotenoid pigment, leakage on fluorescein angiography, blue light-reflectance abnormalities, and intraretinal cysts and ellipsoid zone defects on optical coherence tomography (OCT). His father and sister had similar ocular findings, although the features in the sister were milder. None of these patients had received serine supplementation. All 3 patients had also been diagnosed clinically with a peripheral neuropathy, although details of the neuropathy were not provided. After exome sequencing identified the SPTLC1 mutation in this family, Gantner et al. (2019) examined additional patients with HSAN1 for macular telangiectasia. Five patients from family 2 and an unrelated woman (patient 1), all of whom also carried the C133Y SPTLC1 mutation, were similarly affected. The individuals from family 2 and patient 1 had received serine supplementation. Two additional unrelated patients (patients 2 and 3), who had HSAN1A due to a heterozygous C133W mutation in the SPTLC1 gene (605712.0002), did not have macular telangiectasia. However, both patients were under the age of 50 and had been treated with serine supplementation. Two patients from another family (family 3) with HSAN1C (613610) due to a heterozygous S384F missense mutation in the SPTLC2 gene (605713.0005) also had macular telangiectasia; they had not received serine supplementation. Gantner et al. (2019) noted that the macular phenotype in patients with HSAN1A and HSAN1C was typical of that observed in those with isolated macular telangiectasia. Moreover, previous studies (see, e.g., Penno et al., 2010, Rotthier et al., 2010, Bode et al., 2016) had demonstrated that mutations in these genes result in abnormal accumulation of neurotoxic deoxysphingolipids. There was a dose-response effect. Studies in mouse models and in cell-based retinal organoids demonstrated that low serine levels were associated with increased deoxysphingolipids that were toxic to photoreceptor cells in the retina and caused peripheral sensory deficits; the main neurotoxic species was identified as deoxydihydroceramide. Overall, the findings provided a link between altered serine and lipid metabolism, whether caused by an identified genetic defect or unknown factors, and peripheral neuropathy as well as macular telangiectasia type 2.


Inheritance

The transmission pattern of HSAN1A in the families reported by Dawkins et al. (2001) was consistent with autosomal dominant inheritance.


Mapping

Nicholson et al. (1996) undertook a genomewide linkage screen in 4 Australian kindreds with hereditary sensory neuropathy, including 1 family that had been reported by Jackson (1949) and followed up by Wallace (1968, 1970). Nicholson et al. (1996) found that the disease locus, which they symbolized HSN1, mapped to an 8-cM region flanked by D9S318 and D9S176 on 9q22.1-q22.3. Multipoint linkage analysis suggested a most likely location at D9S287, within a 4.9-cM confidence interval.

Blair et al. (1997) refined the mapping of HSN1 to a 3- to 4-cM interval within the 9q22.1-q22.3 region, and excluded GAS1 (139185) and XPA (611153) as candidate genes. Using composite mapping data, Blair et al. (1998) estimated the HSN1 critical region, flanked by D9S1781 and FB19B7, at 3 to 4 Mb.


Pathogenesis

In studies of Chinese hamster ovary (CHO) cells and yeast, Gable et al. (2010) demonstrated that the mutant SPTLC1 C133W protein (605712.0002) provided sufficient SPT activity to support growth, although total enzyme activity was only 10 to 20% of wildtype. Yeast and CHO cells expressing the C133W mutant along with SPTLC2 (605713) and SSSPTA (613540) or SSSPTB (610412) showed a preferential condensation of palmitoyl-CoA to alanine rather than serine. These results were not found with wildtype SPTLC1. Kinetic studies showed that the mutant protein had the same affinity to serine as the wildtype protein, but a lower Vmax for serine. These results suggested that the mutation perturbs the active site of the protein, facilitating the formation of alanine condensation products. However, small increases in extracellular serine levels were able to inhibit the reaction with alanine. The palmitoyl-CoA/alanine product, 1-deoxysphinganine (1-deoxySa), was shown to increased endoplasmic reticulum stress and the unfolded protein response, which may ultimately be toxic to neurons. Gable et al. (2010) concluded that their findings were consistent with a gain of function that is responsible for the HSAN1 phenotype.

SPT catalyzes the condensation of serine and palmitoyl-CoA, the initial step in the de novo synthesis of sphingolipids. Penno et al. (2010) showed that HSAN1A-related mutations in the SPTLC1 gene induced a shift in the substrate specificity of SPT, which leads to the formation of 2 atypical deoxysphingoid bases: 1-deoxysphinganine from condensation with alanine and 1-deoxymethylsphinganine from condensation with glycine. Neither of these metabolites can be converted to complex sphingolipids or degraded, resulting in their intracellular accumulation. These atypical agents showed pronounced neurotoxic effects on neurite formation in cultured sensory neurons, and was associated with disturbed neurofilament structure. Penno et al. (2010) found increased levels of these atypical agents in lymphocytes and plasma of HSAN1A patients with different SPTLC1 mutations. The findings indicated that HSAN1 results from gain-of-function mutations that cause the formation of atypical and neurotoxic sphingolipid metabolites, rather than from lack of de novo sphingolipid synthesis.


Molecular Genetics

In all affected members of 11 families with HSAN1A, Dawkins et al. (2001) identified heterozygous missense mutations in the SPTLC1 gene (C133Y, 605712.0001; C133W, 605712.0002; V144D, 605712.0003). Four of the families had previously been reported by Nicholson et al. (1996), including the multigenerational Australian family originally reported by Jackson (1949) and followed up by Wallace (1968, 1970).

Bejaoui et al. (2001) independently identified 2 of the same SPTLC1 mutations in 2 unrelated families with HSN1.

In twin sisters with HSN1 from a Belgian family originally reported by Montanini (1958), Verhoeven et al. (2004) identified a mutation in the SPTLC1 gene (G387A; 605712.0004).

The findings of Hornemann et al. (2009) cast doubt on the pathogenicity of the G387A mutation. By in vitro functional expression assays in HEK293 cells, Hornemann et al. (2009) found that none of the 4 SPTLC1 mutations, C133Y, C133W, V144D, or G387A, interfered with formation of the SPT complex. The first 3 mutant proteins resulted in 40 to 50% decreased SPT activity, but the G387A protein showed no effect on SPT activity. Further studies showed that the G387A protein could rescue a SPTLC1-deficient cell line. Finally, Hornemann et al. (2009) identified an unaffected woman who was homozygous for the G387A mutation, suggesting that it is not pathogenic. Hornemann et al. (2009) postulated that the G387A variant, and perhaps the other 3 SPTLC1 variants previously associated with HSN1, may not be directly disease-causing, but rather have an indirect or bystander effect by increasing the risk for HSN1 in conjunction with another mutation.

Three patients with a severe form of HSAN1 were heterozygous for mutations at the same codon in the SPTLC1 gene (S331F, 605712.0005 and S331Y, 605712.0007) (Rotthier et al., 2009; Auer-Grumbach et al., 2013).


Genotype/Phenotype Correlations

Using biochemical assays in transfected cells, Bode et al. (2016) assessed the enzymatic activity and biochemical consequences of 11 different missense variants in the SPTLC1 gene, including 7 that had previously been identified in HSAN1A patients. None of the variants resulted in a loss of activity, as had previously been suggested. Several variants, including V144D, A310G, A339V, and A352V, showed no change in canonical enzyme activity and did not form increased levels of neurotoxic 1-deoxySL compounds. The authors suggested that these variants are not pathogenic and may not be causative of the phenotype. Two mutations, C133Y and C133W, were associated with increased 1-deoxySL levels compared to wildtype, but had unaltered canonical activity. These mutations were associated with a typical late-onset phenotype with primarily sensory and mild motor impairment. Two mutations, S331F and S331Y, were characterized by increased canonical enzyme activity as well as increased formation of C18-, 1-deoxy-, and C20-sphingoid bases, the latter of which was a unique and particular hallmark of these mutations. These mutations were associated with a severe phenotype characterized by early onset of symptoms, autonomic impairment, and juvenile cataracts. Further studies showed that the formation of toxic 1-deoxySL in animal models and patients with HSAN1 was reduced by increased availability of serine through oral supplementation. In contrast, increased availability of alanine resulted in augmented 1-deoxySL formation and aggravated neuropathic symptoms.


Population Genetics

Nicholson et al. (2001) found that 3 Australian families of English extraction and 3 English families with HSAN1A had the same SPTLC1 mutation (605712.0002), the same chromosome 9 haplotype, and the same phenotype. They therefore concluded that the Australian and English families had the same founder who, on the basis of historical information, lived in southern England before 1800. The phenotype caused by this mutation is the same as that in the English families of Campbell and Hoffman (1964) and possibly in the original English family of Hicks (1922).


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  32. Rotthier, A., Baets, J., De Vriendt, E., Jacobs, A., Auer-Grumbach, M., Levy, N., Bonello-Palot, N., Kilic, S. S., Weis, J., Nascimento, A., Swinkels, M., Kruyt, M. C., Jordanova, A., De Jonghe, P., Timmerman, V. Genes for hereditary sensory and autonomic neuropathies: a genotype-phenotype correlation. Brain 132: 2699-2711, 2009. [PubMed: 19651702, images, related citations] [Full Text]

  33. Schultze, F. Familiaer auftretendes malum perforans der Fuesse (familiaere lumbale Syringomyelie). Dtsch. Med. Wschr. 43: 545-547, 1917.

  34. Silverman, F. N., Gilden, J. J. Congenital insensitivity to pain, a neurologic syndrome with bizarre skeletal lesions. Radiology 72: 176-190, 1959. [PubMed: 13634374, related citations] [Full Text]

  35. Smith, E. M. Familial neurotrophic osseous atrophy: a familial neurotrophic condition of the feet with anesthesia and loss of bone. JAMA 102: 593-595, 1934.

  36. Tocantins, L. M., Reimann, H. A. Perforating ulcers of feet, with osseous atrophy in family with other evidences of dysgenesis (hare lip, cleft palate): an instance of probable myelodysplasia. JAMA 112: 2251-2255, 1939.

  37. Verhoeven, K., Coen, K., De Vriendt, E., Jacobs, A., Van Gerwen, V., Smouts, I., Pou-Serradell, A., Martin, J.-J., Timmerman, V., De Jonghe, P. SPTLC1 mutation in twin sisters with hereditary sensory neuropathy type I. Neurology 62: 1001-1002, 2004. [PubMed: 15037712, related citations] [Full Text]

  38. Wallace, D. C. A Study of an Hereditary Neuropathy. Thesis: Univ. of Sydney (pub.) 1968.

  39. Wallace, D. C. Hereditary sensory radicular neuropathy. In: Archdall Medical Monograph 8. Sydney: Australasian Med. Pub. Co. 1970.


Cassandra L. Kniffin - updated : 11/04/2019
Carol A. Bocchini - updated : 10/22/2019
Cassandra L. Kniffin - updated : 11/12/2010
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# 162400

NEUROPATHY, HEREDITARY SENSORY AND AUTONOMIC, TYPE IA; HSAN1A


Alternative titles; symbols

HSAN IA
HSAN1
NEUROPATHY, HEREDITARY SENSORY, TYPE IA; HSN1A
HSN IA
NEUROPATHY, HEREDITARY SENSORY RADICULAR, AUTOSOMAL DOMINANT, TYPE 1A


SNOMEDCT: 230553002, 397734008, 860813007;   ORPHA: 36386;   DO: 0070152;  


Phenotype-Gene Relationships

Location Phenotype Phenotype
MIM number
Inheritance Phenotype
mapping key
Gene/Locus Gene/Locus
MIM number
9q22.31 Neuropathy, hereditary sensory and autonomic, type IA 162400 Autosomal dominant 3 SPTLC1 605712

TEXT

A number sign (#) is used with this entry because hereditary sensory neuropathy type IA (HSAN1A) is caused by heterozygous mutation in the SPTLC1 gene (605712) on chromosome 9q22.


Description

Hereditary sensory and autonomic neuropathy type IA (HSAN1A) is an autosomal dominant neurologic disorder characterized by sensory neuropathy with variable autonomic and motor involvement. Most patients have adult onset of slowly progressive distal sensory impairment manifest as numbness, tingling, or pain, as well as distal muscle atrophy. Complications include ulceration and osteomyelitis. Some patients may have a more severe phenotype with onset in childhood. Electrophysiologic studies show a predominantly axonal neuropathy with some demyelinating features. Some patients may have evidence of central nervous system involvement, including macular telangiectasia type 2. Affected individuals have increased levels of plasma 1-deoxysphingolipids (1-deoxySLs), which are thought to be neurotoxic (summary by Rotthier et al., 2010 and Gantner et al., 2019). Oral supplementation with serine decreases 1-deoxySL and may offer some clinical benefits (Fridman et al., 2019).

Genetic Heterogeneity of Hereditary Sensory and Autonomic Neuropathy

See also HSAN1C (613640), caused by mutation in the SPTLC2 gene (605713) on 14q24; HSN1D (613708), caused by mutation in the ATL1 gene (606439) on 14q22; HSN1E (614116), caused by mutation in the DNMT1 gene (126375) on 19p13; HSN1F (615632), caused by mutation in the ATL3 gene (609369) on 11q13; HSAN2A (201300), caused by mutation in the HSN2 isoform of the WNK1 gene (605232) on 12p13; HSAN2B (613115), caused by mutation in the FAM134B gene (613114) on 5p15; HSN2C (614213), caused by mutation in the KIF1A gene (601255) on 2q37; HSAN2D (see 243000), caused by mutation in the SCN9A gene (603415) on 2q24; HSAN3 (223900), caused by mutation in the ELP1 gene (603722) on 9q31; HSAN4 (256800), caused by mutation in the NTRK1 gene (191315) on 1q23; HSAN5 (608654), caused by mutation in the NGF gene (162030) on 1p13; HSAN6 (614653), caused by mutation in the DST gene (113810) on 6p12; HSAN7 (615548), caused by mutation in the SCN11A gene (604385) on 3p22; and HSAN8 (616488), caused by mutation in the PRDM12 gene (616458) on chromosome 9q34.

Adult-onset HSAN with anosmia (608720) may be another distinct form of HSAN, and HSAN1B (608088) with cough and gastroesophageal reflux maps to chromosome 3p24-p22.


Clinical Features

Hicks (1922) described an English family in which 10 members suffered from perforating ulcers of the feet, shooting pains, and deafness. Age of onset ranged from 15 to 36 years. Presentation was usually with a corn on a big toe followed by a painless ulcer with bony debris. Patients later experienced shooting pains similar to the lightning pains of tabes dorsalis and developed bilateral deafness progressing to total deafness over several years. Neurologic examination showed disappearance of ankle and knee jerks and absence of an extensor plantar response. There was loss of pain, touch, heat, and cold sensation over the feet, but sensation of the arms remained normal. Cranial nerves were normal, with the exception of the auditory nerve, pupils reacted normally, and there was no nystagmus. Hicks (1922) noted that although hereditary perforating ulcers of the feet had been reported in patients in the past, there had been no previous mention of accompanying deafness or shooting pains. Denny-Brown (1951) reported the clinical and autopsy findings of a 53-year-old woman who was a member of the family reported by Hicks (1922). When she was 22 years of age, an ulcer formed on her right great toe, requiring a year to heal. She subsequently suffered from recurrent ulceration, each episode lasting 6 to 9 months and sometimes extending to bone. In her early twenties, she first noticed shooting pains in her legs, sometimes in her arms. Deafness began at the age of 40 years and progressed to almost total deafness by 53 years of age. Neurologic examination at 53 years of age showed loss of all sensation in the lower legs, with loss of pain and temperature sensation in the thighs and hands. Autopsy showed a small brain and marked loss of ganglion cells in the sacral and lumbar dorsal root ganglia. Remaining ganglion cells showed proliferation of subcapsular dendrites and hyaline bodies, possibly representing an amyloid mass around capillaries. There were less severe changes in C-8 and T-1 ganglia. The affected families reported by Ervin and Sternbach (1960) and Silverman and Gilden (1959) appeared to show autosomal dominant inheritance. Mandell and Smith (1960) observed sensory radicular neuropathy in 3 generations of a family. Clinical features included neuropathic arthropathy, recurrent ulceration of the lower extremities, and signs of radicular sensory deficiency in both the upper and the lower extremities without any motor dysfunction. Dyck et al. (1965) described a family with sensory neuropathy accompanied by peroneal muscular atrophy and pes cavus. Campbell and Hoffman (1964) and DeLeon (1969) also reported cases in which amyotrophy was a feature. Using a cholinesterase technique on skin biopsies from the pad of the great toe of affected persons, Dyck et al. (1965) found normal numbers of Meissner corpuscles in a 14-year-old boy with early signs suggestive of the disorder, but no corpuscles in a 37-year-old man and a 28-year-old woman with well-developed disease.

Dyck et al. (1983) noted that 'burning feet' may be the only manifestation of dominantly inherited sensory neuropathy. The symptoms are ameliorated by cold and aggravated by heat. Restless legs and lancinating pain are other presentations of the disorder, which often resulted in severe distal sensory loss, mutilating acropathy, and neurotrophic arthropathy.

In a detailed clinical study of a patient with HSN1, including audiometric testing, autonomic functions, electromyography, transcranial magnetic stimulation, and brain imaging, Hageman et al. (1992) determined that there were no signs of central nervous system involvement and stated that HSN1 is a disorder of the dorsal root ganglia and peripheral nerves.

Wallace (1968, 1970) studied an extensively affected Australian kindred. In a study of this kindred and 3 other Australian kindreds with HSAN1, Nicholson et al. (1996) found that a typical history included lightning pains, painless skin injuries and ulceration, and signs including distal sensory loss to sharp, hot, and cold sensation, with loss of distal reflexes and distal muscle wasting. Nerve conduction velocities showed an axonal neuropathy, particularly of the lower limbs.

Dubourg et al. (2000) reported a French family with autosomal dominant hereditary sensory neuropathy suggestive of linkage to chromosome 9q. Mean age at onset was 34 years. All patients presented with distal sensory loss and distal muscle weakness of both the upper and lower limbs. Four patients had foot ulcerations, and 3 patients had hyperhidrosis. Motor nerve conduction velocities were normal or mildly decreased, consistent with an axonal neuropathy. Sensory nerve action potentials were either reduced or could not be recorded.

Severe Phenotype

Rotthier et al. (2009) reported a French Gypsy patient with an unusually severe form of HSAN1. The patient had congenital insensitivity to pain with eschar and foot ulceration, pes cavus/equinovarus, vocal cord paralysis, and gastroesophageal reflux. The patient also had severe growth and mental retardation, microcephaly, hypotonia, amyotrophy, and respiratory insufficiency. Nerve conduction studies showed absent sensory and motor responses in the upper and lower limbs. Genetic analysis identified a de novo heterozygous mutation in the SPTLC1 gene (S331F; 605712.0005). The phenotype expanded the clinical spectrum of HSAN1.

Auer-Grumbach et al. (2013) reported that a patient (ER-CIPA-20374) described by Huehne et al. (2008) with a severe form of HSAN1 had the same heterozygous S331F mutation in the SPTLC1 gene as that reported by Rotthier et al. (2009) in a patient with early-onset severe HSAN1A. The patient described by Huehne et al. (2008) and Auer-Grumbach et al. (2013) had onset in early childhood or muscle weakness and hypotrophy in addition to prominent sensory disturbances, bone fractures, and osteomyelitis. The patient developed cataract at age 9 years, complete retinal detachment at age 10, and repetitive corneal ulceration and keratitis with poor wound healing.

In another patient with a severe form of HSAN1, Auer-Grumbach et al. (2013) identified a different de novo heterozygous mutation at the same codon (S331Y; 605712.0007). This patient had onset at age 4 years of unsteady gait, hand tremor, mild sensory disturbances, and a pes cavus foot deformity necessitating triple arthrodesis at age 5. At examination at age 12, there was general muscle hypotrophy and hypotonia with pronounced weakness in the distal muscles of the upper and lower limbs. There were prominent sensory disturbances; these were pronounced in the feet and affected all qualities except for the vibration sense, which remained completely preserved. At the toes, scars from burns due to reduced pain and temperature sensation were evident. There was also hypermobility of the joints, bilateral hand tremor, and fasciculations, most prominent in the tongue. At age 13, she developed bilateral cataracts. Disease progression was rapid and led to severe scoliosis, respiratory problems, and wheelchair dependence at age 14. The patient had prominent growth retardation but normal intellectual development. The level of 1-deoxySL was significantly elevated in the patient's plasma.

Association with Macular Telangiectasia Type 2

Gantner et al. (2019) identified 9 patients, including 8 patients from 2 unrelated families and an additional unrelated patient, with genetically confirmed HSAN1A who also had type 2 macular telangiectasia. All carried the same heterozygous C133Y mutation in the SPTLC1 gene (605712.0001). The proband in the first family presented with bilateral bull's eye maculopathy at 21 years of age. Detailed ophthalmologic examination showed findings diagnostic for macular telangiectasia type 2, including parafoveal telangiectatic retinal vessels, 'right angle' venules, retinal opacification, pigment clumping, low levels of macular carotenoid pigment, leakage on fluorescein angiography, blue light-reflectance abnormalities, and intraretinal cysts and ellipsoid zone defects on optical coherence tomography (OCT). His father and sister had similar ocular findings, although the features in the sister were milder. None of these patients had received serine supplementation. All 3 patients had also been diagnosed clinically with a peripheral neuropathy, although details of the neuropathy were not provided. After exome sequencing identified the SPTLC1 mutation in this family, Gantner et al. (2019) examined additional patients with HSAN1 for macular telangiectasia. Five patients from family 2 and an unrelated woman (patient 1), all of whom also carried the C133Y SPTLC1 mutation, were similarly affected. The individuals from family 2 and patient 1 had received serine supplementation. Two additional unrelated patients (patients 2 and 3), who had HSAN1A due to a heterozygous C133W mutation in the SPTLC1 gene (605712.0002), did not have macular telangiectasia. However, both patients were under the age of 50 and had been treated with serine supplementation. Two patients from another family (family 3) with HSAN1C (613610) due to a heterozygous S384F missense mutation in the SPTLC2 gene (605713.0005) also had macular telangiectasia; they had not received serine supplementation. Gantner et al. (2019) noted that the macular phenotype in patients with HSAN1A and HSAN1C was typical of that observed in those with isolated macular telangiectasia. Moreover, previous studies (see, e.g., Penno et al., 2010, Rotthier et al., 2010, Bode et al., 2016) had demonstrated that mutations in these genes result in abnormal accumulation of neurotoxic deoxysphingolipids. There was a dose-response effect. Studies in mouse models and in cell-based retinal organoids demonstrated that low serine levels were associated with increased deoxysphingolipids that were toxic to photoreceptor cells in the retina and caused peripheral sensory deficits; the main neurotoxic species was identified as deoxydihydroceramide. Overall, the findings provided a link between altered serine and lipid metabolism, whether caused by an identified genetic defect or unknown factors, and peripheral neuropathy as well as macular telangiectasia type 2.


Inheritance

The transmission pattern of HSAN1A in the families reported by Dawkins et al. (2001) was consistent with autosomal dominant inheritance.


Mapping

Nicholson et al. (1996) undertook a genomewide linkage screen in 4 Australian kindreds with hereditary sensory neuropathy, including 1 family that had been reported by Jackson (1949) and followed up by Wallace (1968, 1970). Nicholson et al. (1996) found that the disease locus, which they symbolized HSN1, mapped to an 8-cM region flanked by D9S318 and D9S176 on 9q22.1-q22.3. Multipoint linkage analysis suggested a most likely location at D9S287, within a 4.9-cM confidence interval.

Blair et al. (1997) refined the mapping of HSN1 to a 3- to 4-cM interval within the 9q22.1-q22.3 region, and excluded GAS1 (139185) and XPA (611153) as candidate genes. Using composite mapping data, Blair et al. (1998) estimated the HSN1 critical region, flanked by D9S1781 and FB19B7, at 3 to 4 Mb.


Pathogenesis

In studies of Chinese hamster ovary (CHO) cells and yeast, Gable et al. (2010) demonstrated that the mutant SPTLC1 C133W protein (605712.0002) provided sufficient SPT activity to support growth, although total enzyme activity was only 10 to 20% of wildtype. Yeast and CHO cells expressing the C133W mutant along with SPTLC2 (605713) and SSSPTA (613540) or SSSPTB (610412) showed a preferential condensation of palmitoyl-CoA to alanine rather than serine. These results were not found with wildtype SPTLC1. Kinetic studies showed that the mutant protein had the same affinity to serine as the wildtype protein, but a lower Vmax for serine. These results suggested that the mutation perturbs the active site of the protein, facilitating the formation of alanine condensation products. However, small increases in extracellular serine levels were able to inhibit the reaction with alanine. The palmitoyl-CoA/alanine product, 1-deoxysphinganine (1-deoxySa), was shown to increased endoplasmic reticulum stress and the unfolded protein response, which may ultimately be toxic to neurons. Gable et al. (2010) concluded that their findings were consistent with a gain of function that is responsible for the HSAN1 phenotype.

SPT catalyzes the condensation of serine and palmitoyl-CoA, the initial step in the de novo synthesis of sphingolipids. Penno et al. (2010) showed that HSAN1A-related mutations in the SPTLC1 gene induced a shift in the substrate specificity of SPT, which leads to the formation of 2 atypical deoxysphingoid bases: 1-deoxysphinganine from condensation with alanine and 1-deoxymethylsphinganine from condensation with glycine. Neither of these metabolites can be converted to complex sphingolipids or degraded, resulting in their intracellular accumulation. These atypical agents showed pronounced neurotoxic effects on neurite formation in cultured sensory neurons, and was associated with disturbed neurofilament structure. Penno et al. (2010) found increased levels of these atypical agents in lymphocytes and plasma of HSAN1A patients with different SPTLC1 mutations. The findings indicated that HSAN1 results from gain-of-function mutations that cause the formation of atypical and neurotoxic sphingolipid metabolites, rather than from lack of de novo sphingolipid synthesis.


Molecular Genetics

In all affected members of 11 families with HSAN1A, Dawkins et al. (2001) identified heterozygous missense mutations in the SPTLC1 gene (C133Y, 605712.0001; C133W, 605712.0002; V144D, 605712.0003). Four of the families had previously been reported by Nicholson et al. (1996), including the multigenerational Australian family originally reported by Jackson (1949) and followed up by Wallace (1968, 1970).

Bejaoui et al. (2001) independently identified 2 of the same SPTLC1 mutations in 2 unrelated families with HSN1.

In twin sisters with HSN1 from a Belgian family originally reported by Montanini (1958), Verhoeven et al. (2004) identified a mutation in the SPTLC1 gene (G387A; 605712.0004).

The findings of Hornemann et al. (2009) cast doubt on the pathogenicity of the G387A mutation. By in vitro functional expression assays in HEK293 cells, Hornemann et al. (2009) found that none of the 4 SPTLC1 mutations, C133Y, C133W, V144D, or G387A, interfered with formation of the SPT complex. The first 3 mutant proteins resulted in 40 to 50% decreased SPT activity, but the G387A protein showed no effect on SPT activity. Further studies showed that the G387A protein could rescue a SPTLC1-deficient cell line. Finally, Hornemann et al. (2009) identified an unaffected woman who was homozygous for the G387A mutation, suggesting that it is not pathogenic. Hornemann et al. (2009) postulated that the G387A variant, and perhaps the other 3 SPTLC1 variants previously associated with HSN1, may not be directly disease-causing, but rather have an indirect or bystander effect by increasing the risk for HSN1 in conjunction with another mutation.

Three patients with a severe form of HSAN1 were heterozygous for mutations at the same codon in the SPTLC1 gene (S331F, 605712.0005 and S331Y, 605712.0007) (Rotthier et al., 2009; Auer-Grumbach et al., 2013).


Genotype/Phenotype Correlations

Using biochemical assays in transfected cells, Bode et al. (2016) assessed the enzymatic activity and biochemical consequences of 11 different missense variants in the SPTLC1 gene, including 7 that had previously been identified in HSAN1A patients. None of the variants resulted in a loss of activity, as had previously been suggested. Several variants, including V144D, A310G, A339V, and A352V, showed no change in canonical enzyme activity and did not form increased levels of neurotoxic 1-deoxySL compounds. The authors suggested that these variants are not pathogenic and may not be causative of the phenotype. Two mutations, C133Y and C133W, were associated with increased 1-deoxySL levels compared to wildtype, but had unaltered canonical activity. These mutations were associated with a typical late-onset phenotype with primarily sensory and mild motor impairment. Two mutations, S331F and S331Y, were characterized by increased canonical enzyme activity as well as increased formation of C18-, 1-deoxy-, and C20-sphingoid bases, the latter of which was a unique and particular hallmark of these mutations. These mutations were associated with a severe phenotype characterized by early onset of symptoms, autonomic impairment, and juvenile cataracts. Further studies showed that the formation of toxic 1-deoxySL in animal models and patients with HSAN1 was reduced by increased availability of serine through oral supplementation. In contrast, increased availability of alanine resulted in augmented 1-deoxySL formation and aggravated neuropathic symptoms.


Population Genetics

Nicholson et al. (2001) found that 3 Australian families of English extraction and 3 English families with HSAN1A had the same SPTLC1 mutation (605712.0002), the same chromosome 9 haplotype, and the same phenotype. They therefore concluded that the Australian and English families had the same founder who, on the basis of historical information, lived in southern England before 1800. The phenotype caused by this mutation is the same as that in the English families of Campbell and Hoffman (1964) and possibly in the original English family of Hicks (1922).


See Also:

Clarke and Groves (1909); Danon and Carpenter (1985); Miller et al. (1976); Ogryzlo (1946); Schultze (1917); Smith (1934); Tocantins and Reimann (1939)

REFERENCES

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Contributors:
Cassandra L. Kniffin - updated : 11/04/2019
Carol A. Bocchini - updated : 10/22/2019
Cassandra L. Kniffin - updated : 11/12/2010
Cassandra L. Kniffin - updated : 9/23/2010
Cassandra L. Kniffin - updated : 5/14/2009
Cassandra L. Kniffin - updated : 2/6/2009
Cassandra L. Kniffin - updated : 9/1/2005
Cassandra L. Kniffin - updated : 5/18/2004
Denise L. M. Goh - updated : 4/10/2003
Carol A. Bocchini - reorganized : 10/5/2001
Victor A. McKusick - updated : 9/27/2001
Ada Hamosh - updated : 3/2/2001
Sheryl A. Jankowski - updated : 12/22/1998
Victor A. McKusick - updated : 12/2/1997

Creation Date:
Victor A. McKusick : 6/2/1986

Edit History:
carol : 04/02/2021
carol : 11/23/2020
carol : 11/04/2019
ckniffin : 11/04/2019
carol : 10/28/2019
carol : 10/25/2019
carol : 10/23/2019
carol : 10/22/2019
carol : 07/12/2017
carol : 07/11/2017
carol : 10/13/2016
carol : 05/13/2016
alopez : 7/29/2015
ckniffin : 7/28/2015
carol : 11/19/2014
carol : 11/10/2014
ckniffin : 10/28/2014
ckniffin : 2/10/2014
carol : 12/4/2013
ckniffin : 12/3/2013
alopez : 5/29/2012
ckniffin : 5/29/2012
carol : 9/16/2011
ckniffin : 9/15/2011
alopez : 7/29/2011
ckniffin : 7/27/2011
wwang : 2/23/2011
ckniffin : 1/28/2011
carol : 11/16/2010
ckniffin : 11/12/2010
wwang : 10/6/2010
ckniffin : 9/23/2010
terry : 12/16/2009
terry : 6/3/2009
wwang : 5/27/2009
ckniffin : 5/14/2009
wwang : 2/6/2009
terry : 2/3/2009
carol : 7/12/2007
wwang : 9/6/2005
ckniffin : 9/1/2005
ckniffin : 8/17/2005
tkritzer : 9/8/2004
ckniffin : 8/27/2004
alopez : 8/17/2004
terry : 7/27/2004
tkritzer : 6/11/2004
carol : 5/21/2004
ckniffin : 5/18/2004
ckniffin : 5/18/2004
cwells : 11/5/2003
carol : 4/29/2003
carol : 4/10/2003
carol : 10/5/2001
carol : 10/5/2001
mcapotos : 10/4/2001
terry : 9/27/2001
alopez : 3/2/2001
terry : 3/2/2001
carol : 10/22/1999
psherman : 1/6/1999
psherman : 12/22/1998
carol : 7/8/1998
carol : 5/20/1998
mark : 12/10/1997
terry : 12/2/1997
randy : 8/31/1996
terry : 5/14/1996
terry : 5/6/1996
mimadm : 12/2/1994
terry : 7/15/1994
warfield : 4/21/1994
carol : 10/26/1993
carol : 8/31/1993
supermim : 3/16/1992