Alternative titles; symbols
SNOMEDCT: 721879006; ORPHA: 2556; DO: 0111808;
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
Gene/Locus |
Gene/Locus MIM number |
|---|---|---|---|---|---|---|
| Xp22.2 | Linear skin defects with multiple congenital anomalies 1 | 309801 | X-linked dominant | 3 | HCCS | 300056 |
A number sign (#) is used with this entry because of evidence that linear skin defects with multiple congenital anomalies, also known as microphthalmia with linear skin defects (MLS) and MIDAS syndrome, is caused by mutation in the HCCS gene (300056) on chromosome Xp22.
The microphthalmia with linear skin defects syndrome (MLS) is an X-linked dominant disorder characterized by unilateral or bilateral microphthalmia and linear skin defects--which are limited to the face and neck, consisting of areas of aplastic skin that heal with age to form hyperpigmented areas--in affected females and in utero lethality for males (Wimplinger et al., 2006).
Genetic Heterogeneity of Linear Skin Defects with Multiple Congenital Anomalies
Also see LSDMCA2 (300887), caused by mutation in the COX7B gene (300885) on Xq21, and LSDMCA3 (300952), caused by mutation in the NDUFB11 gene (300403) on Xp11.3.
In 2 females with de novo X;Y translocations, Al Gazali et al. (1990) described manifestations including irregular linear areas of erythematous skin hypoplasia involving the head and neck, along with eye findings that included microphthalmia, corneal opacities, and orbital cysts. The features were considered distinct from those of either focal dermal hypoplasia (FDH; 305600) or incontinentia pigmenti (308300). Cytogenetic analysis showed that the breakpoint in the X chromosome was at Xp22.3 in both females. Al Gazali et al. (1990) suggested that deletion or disruption of DNA sequences in the region of Xp22.3 was responsible for this syndrome. It had been suggested that focal dermal hypoplasia maps to the same region, Xp22.31. Temple et al. (1990) reported a third case with a terminal deletion of Xpter-p22.2. Allanson and Richter (1991) reported a newborn female with identical skin findings of the head and neck, bilateral microphthalmia, and corneal opacities; the terminal deletion of the X chromosome with breakpoint at Xp22.2 was also present. Diaphragmatic hernia, causing severe respiratory distress, led to death after unsuccessful surgical repair. Necropsy showed absence of the septum pellucidum with an ectopic area of gray and white matter. The mother was found to have an identical terminal deletion of the X chromosome with the breakpoint at Xp22.2. She was of normal intelligence but her height was less than the 3rd centile. She had depigmented patches of skin visible either with the naked eye or with ultraviolet light, and 3 of 4 wisdom teeth were unerupted. This disorder is presumably lethal in the hemizygous male (Ballabio, 1993).
Happle et al. (1993) reported an affected female with this disorder, which they called MIDAS (microphthalmia, dermal aplasia, and sclerocornea) syndrome, who died at age 9 months from cardiomyopathy resulting in ventricular fibrillation. Happle et al. (1993) maintained that MIDAS syndrome is distinct from FDH and noted that deletion at Xp22.3 has never been demonstrated in typical cases of FDH, but only in cases with the MIDAS complex. They argued that, in contrast to FDH, the aplastic skin lesions of the MIDAS syndrome are limited to the upper half of the body, often involving the face and neck exclusively, and they do not show herniation of fatty tissue. Moreover, several other manifestations of FDH, such as perioral papillomatous lesions, clefting of the hands or feet, syndactyly, and coloboma are absent in MIDAS syndrome. They contended that these marked clinical differences supported the notion that the gene for FDH could not be assigned to Xp22.3 or to a neighboring locus.
Lindsay et al. (1994) described the clinical, cytogenetic, and molecular characteristics of 3 patients with MLS. In 2 of them, females, a terminal Xpter-p22.2 deletion was present. One of these 2 patients had an aborted fetus with anencephaly and the same chromosome anomaly. The third patient was an XX male with an Xp/Yp exchange spanning the SRY gene (480000), resulting in distal Xp monosomy. Extensive clinical variability observed in these patients and the results of molecular analysis suggested that X inactivation plays an important role in determining the phenotype of the MLS syndrome. They proposed that MLS, Aicardi syndrome (AIC; 304050), and Goltz syndrome (FDH) are due to involvement of the same gene or genes, and the different patterns of X inactivation are responsible for the phenotypic differences observed in the 3 disorders. However, they could not rule out that each component of the MLS phenotype is caused by deletion of a different gene, i.e., that MLS represents a contiguous gene syndrome.
Mucke et al. (1995) described MIDAS syndrome in a mother and her daughter who showed strikingly similar features. The daughter was pictured at age 2 years with bilateral microphthalmia and sclerocornea. Bilateral anterior chamber eye anomaly had caused glaucoma, resulting in a spontaneous perforation on the right side. At the age of 11, the patient was found to have hypertrophy of the clitoris with a normal vagina and rudimentary uterus as well as a dysgenetic testis on the right and an ovotestis on the left. The mother, who was blind, had linear skin defects in the mandibular area similar to those in the daughter. Corneal opacities were not found in the mother. Mucke et al. (1995) stated that this was the first report of a familial occurrence of definite full-blown MIDAS syndrome. Furthermore, they insisted that MIDAS syndrome is distinct from Goltz syndrome and Aicardi syndrome. They stated that at least 4 of 16 cases of MIDAS syndrome have displayed anomalies of external or internal genitalia. With the exception of 1 XX male, the MIDAS syndrome had so far occurred exclusively in females. An X/Y translocation had been documented in 5 cases, including the 2 patients reported by Mucke et al. (1995). Patients with MIDAS syndrome are often short of stature.
Stratton et al. (1998) reported a second 46,XX male with MIDAS syndrome. In addition to microphthalmia and linear skin streaks, he had a secundum ASD, hypospadias with chordee, anal fistula, and agenesis of the corpus callosum with colpocephaly (dilation of the posterior portions of the lateral ventricles). Biopsy of a linear streak showed smooth muscle hamartomata rather than the presumed dermal aplasia. Detailed ophthalmologic examination did not show retinal lacunae typical of Aicardi syndrome.
Zvulunov et al. (1998) reviewed 21 reported patients with aplasia cutis congenita and microphthalmia. Tabulation of the significant features showed that in addition to the characteristic reticulolinear facial skin defects, which were present in all cases, and microphthalmia, which was present in 18 (86%) of the 21 patients, short stature was another prevalent feature, present in 10 (83%) of the 12 patients for whom stature had been described.
Ogata et al. (1998) described a female infant with microphthalmia with linear skin defects syndrome and monosomy for the Xp22 region. The clinical features included right microphthalmia and sclerocornea, left corneal opacity, linear red rash and scar-like skin lesions on the nose and cheeks, and absence of the corpus callosum.
Sharma et al. (2008) described a female infant with MLS and reviewed 41 previously reported cases. The 16-day-old African American girl had linear pink atrophic plaques that followed Blaschko lines along the left cheek, extending laterally to the ear and inferiorly to the chin, neck, and upper chest; there were also scattered similar lesions on the right cheek and neck. In addition, she had a left preauricular pit and failed her initial hearing test on the left. Although she did not exhibit appreciable microphthalmia, there was a discrete area of opacification of the right cornea, multiple areas of stromal hypopigmentation in both irides, and numerous small patches of hypopigmentation in both fundi. Physical examination at 1 month of age showed rhizomelic and mesomelic shortening of her limbs, with height below the 3rd percentile. Review of previously reported features in cases of MLS showed that linear skin defects were present in 95%, microphthalmia in 83%, and short stature in 74%; features occurring in approximately one-third of patients included corneal clouding or opacities, sclerocornea, developmental delay, and agenesis of the corpus callosum.
Zumwalt et al. (2012) reported a 14-month-old girl who was referred for evaluation of a birthmark, which consisted of brown macules involving the cheeks and extending to the nose and neck. Examination showed that the lesions followed the lines of Blaschko, and there were geographic-shaped atrophic pink lesions within the affected areas. In addition, she had microphthalmia, patent foramen ovale, and profound sensorineural hearing loss. Brain MRI showed agenesis of the corpus callosum, bilateral microphthalmia, colpocephaly, and bilateral periventricular leukomalacia involving the parietooccipital lobes.
MIDAS syndrome is an X-linked dominant disorder, with lethality in the male (Wimplinger et al., 2006).
In a 46,XX male with MIDAS syndrome, Stratton et al. (1998) performed DNA studies with distal Xp-specific probes that indicated a deletion of 1 X chromosome. Fluorescence in situ hybridization studies with X- and Y-specific probes demonstrated the presence of a derivative X chromosome from an X;Y translocation.
In a female infant with MLS, Ogata et al. (1998) performed microsatellite analysis that revealed monosomy for Xp22 involving the critical region for the MLS gene. X-inactivation analysis for the methylation status of the PGK1 gene (311800) indicated the presence of inactive normal X chromosomes. Ogata et al. (1998) concluded that functional absence of the MLS gene caused by inactivation of the normal X chromosome plays a pivotal role in the development of MLS in patients with Xp22 monosomy.
Kono et al. (1999) studied a male infant with bilateral microphthalmia and corneal opacities, hypospadias without evidence of hypogonadism, and Wenckebach conduction disturbance of the heart. High-resolution chromosome analysis revealed a 46,X,del(X)(p22) karyotype, and the phenotype was considered to be MLS without linear skin lesions. PCR and FISH analysis revealed a chromosomal aberration that was designated 46,X,der(X),t(X;Y)(p22.13;q11.2). Chromosomal analysis of the unaffected parents and an unaffected older brother showed normal karyotypes. Kono et al. (1999) noted that despite the absence of skin lesions, the Xp deletion in this patient corresponded to those of previously reported typical cases of MLS. The authors suggested that phenotypic variation in MLS syndrome represents tissue-different X inactivation rather than different genetic effects of 2 contiguous genes.
Anguiano et al. (2003) described twin brothers with microphthalmia, facial dermal hypoplasia, sclerocornea, and supraventricular tachycardia, who were found to have an XX chromosome modality with a subtle Xp/Yp translocation proven by the presence of the SRY gene. The pregnancy was complicated by fetal supraventricular tachycardia, which was prenatally treated with digoxin. Postnatally, both twins required treatment with adenosine, digoxin, and propranolol to remain in normal sinus rhythm. Both twins had selective X inactivation of the derivative X chromosome carrying the Xp/Yp translocation.
In an African American girl with linear skin defects, ocular anomalies but no appreciable microphthalmia, hearing loss, and short stature, Sharma et al. (2008) detected deletion of the short arm of the X chromosome, with a karyotype of 46,X,del(X)(p22.2).
In a 14-month-old girl with microphthalmia, linear skin defects, deafness, and agenesis of the corpus callosum, Zumwalt et al. (2012) identified anomalies at Xp22.3. The chromosomal defect was believed to be de novo, as no other family members demonstrated similar physical findings.
Wapenaar et al. (1993) used cell lines from patients with deletions and translocations involving the Xp22 region to map the loci for ocular albinism type I (OA1; 300500) and MLS. A 2.6-Mb YAC contig spanning the critical regions of these 2 disorders was assembled. Restriction analysis of the contigs established the sizes of the critical regions to be 200 kb for OA1 and 800-925 kb for MLS. Ten potential CpG islands, representing candidate sites for genes, were mapped within the 2.6-Mb region. MLS was found to lie proximal to OA1. Wapenaar et al. (1993) pointed out that other features in these patients, including retinal lacunae, agenesis of the corpus callosum, costovertebral abnormalities, mental retardation, and seizures, overlap with features of the Aicardi syndrome (AIC; 304050) and Goltz syndrome (FDH; 305600), suggesting that different defects in the same gene may be responsible for these 3 disorders.
Kayserili et al. (2001) performed cytogenetic and molecular analysis in a case of MLS and identified the region within which the MLS gene may reside as being a 260-kb interval between the 5-prime end of the MID1 gene (300552) and the 3-prime end of the ARHGAP6 gene (300118).
Using FISH probes and molecular investigations in a mother and daughter with MLS who were originally reported by Mucke et al. (1995), Kotzot et al. (2002) determined the exact physical location of the centromere of the X chromosome and the presence of SRY on 1 X chromosome. In addition, they demonstrated lack of signals for STS (300747) and KAL1 (300836) probes on this X chromosome. Therefore, the breakpoint was mapped proximally to the STS and KAL1 loci. Kotzot et al. (2002) stated that apart from their familial cases, 8 sporadic patients with MLS and a 46,XX,t(X;Y) karyotype had been reported. In all patients the breakpoints were mapped to Xp22.3.
Morleo et al. (2005) reported the clinical, cytogenetic, and molecular characterization of 11 patients, 7 of whom had not been described previously. Chromosomal abnormalities of the short arm of the X chromosome were present in 7 of the patients, 1 of whom displayed an interstitial Xp22.3 deletion. Four patients with clinical features of MLS had apparently normal karyotypes, verified by FISH analysis using genomic clones spanning the MLS minimal critical region, and with genomewide analysis using a 1-Mb resolution BAC microarray. Direct sequencing of coding regions and splice junctions for 3 candidate genes in the critical region, MID1, HCCS, and ARHGAP6, did not reveal any pathogenic changes.
Wimplinger et al. (2006) investigated the family with MLS in which the youngest daughter, who had a classic phenotype and normal karyotype, had previously been studied by Morleo et al. (2005) and no pathogenic mutations had been found in the MID1, HCCS, or ARHGAP6 genes. The eldest daughter of the family had a milder phenotype. The mother, who had no obvious signs of MLS but had a history of skin lesions in infancy that disappeared over time, had 3 miscarriages early in the first trimester and also gave birth to a daughter with bilateral clinical anophthalmia who died at 6 hours. DNA analysis revealed the presence of a heterozygous 8.6-kb deletion encompassing part of the HCCS gene (300056.0001) in the mother and the 2 affected daughters; the deletion was not found in 3 sons or an unaffected daughter. Wimplinger et al. (2006) performed sequence analysis of the HCCS gene in 2 unrelated girls with MLS and normal karyotypes and identified heterozygosity for a de novo nonsense mutation (300056.0002) and a de novo missense mutation (300056.0003), respectively. Noting that cytochrome c is the final product of HCCS activity, Wimplinger et al. (2006) suggested that disturbance of both oxidative phosphorylation and the balance between apoptosis and necrosis, as well as X-inactivation patterns, may contribute to the variable phenotype observed in patients with MLS.
The term 'anophthalmia' has been misused in the medical literature. True or primary anophthalmia is rarely compatible with life; in such cases, the primary optic vesicle has stopped developing and the abnormal development involves major defects in the brain as well (Francois, 1961). The diagnosis can only be made histologically (Reddy et al., 2003; Morini et al., 2005; Smartt et al., 2005), but this is rarely done. In most published cases, the term 'anophthalmia' is used as a synonym for the more appropriate terms 'extreme microphthalmia' or 'clinical anophthalmia.'
Prakash et al. (2002) noted that the gene encoding human holocytochrome c synthase (HCCS; 300056) is located entirely inside the critical region defined for MLS. They generated a deletion mutant in the mouse that inactivated Hccs, whose homologs in lower organisms (cytochrome c or c1 heme lyases) are essential for function of cytochrome c or c1 in the mitochondrial respiratory chain. Ubiquitous deletions generated in vivo led to lethality of hemizygous, homozygous, and heterozygous embryos early in development. This lethality was rescued by expression of the human HCCS gene from a transgenic BAC, resulting in viable homozygous, heterozygous, and hemizygous deleted mice with no apparent phenotype. In the presence of the HCCS transgene, the deletion was easily transmitted to subsequent generations. A single heterozygous deleted female that did not express human HCCS was identified, which is analogous to the low prevalence of the heterozygous MLS deletion in humans. The authors concluded that loss of HCCS causes the male lethality of MLS syndrome.
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Mucke, J., Happle, R., Theile, H. MIDAS syndrome respectively MLS syndrome: a separate entity rather than a particular lyonization pattern of the gene causing Goltz syndrome. (Letter) Am. J. Med. Genet. 57: 117-118, 1995. [PubMed: 7645589] [Full Text: https://doi.org/10.1002/ajmg.1320570123]
Mucke, J., Hoepffner, W., Thamm, B., Theile, H. MIDAS syndrome (microphthalmia, dermal aplasia and sclerocornea): an autonomous entity with linear skin defects within the spectrum of focal hypoplasias. Europ. J. Derm. 5: 197-203, 1995.
Ogata, T., Wakui, K., Muroya, K., Ohashi, H., Matsuo, N., Brown, D. M., Ishii, T., Fukushima, Y. Microphthalmia with linear skin defects syndrome in a mosaic female infant with monosomy for the Xp22 region: molecular analysis of the Xp22 breakpoint and the X-inactivation pattern. Hum. Genet. 103: 51-56, 1998. [PubMed: 9737776] [Full Text: https://doi.org/10.1007/s004390050782]
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