Alternative titles; symbols
SNOMEDCT: 42432003; ORPHA: 90652; DO: 0111784;
| Location | Phenotype |
Phenotype MIM number |
Inheritance |
Phenotype mapping key |
Gene/Locus |
Gene/Locus MIM number |
|---|---|---|---|---|---|---|
| Xq28 | Otopalatodigital syndrome, type II | 304120 | X-linked dominant | 3 | FLNA | 300017 |
A number sign (#) is used with this entry because otopalatodigital syndrome-2 (OPD2) is caused by mutation in the FLNA gene (300017), which encodes filamin A, on chromosome Xq28.
Otopalatodigital syndrome-2 is 1 of 4 otopalatodigital syndromes caused by mutations in the FLNA gene. The disorders, which include frontometaphyseal dysplasia (FMD1; 305620), otopalatodigital syndrome-1 (OPD1; 311300), and Melnick-Needles syndrome (MNS; 309350), constitute a phenotypic spectrum. At the mild end of the spectrum, males with OPD1 have cleft palate and mild skeletal anomalies with conductive deafness caused by ossicular anomalies. FMD is characterized by a generalized skeletal dysplasia, deafness and urogenital defects. Males with OPD2 have disabling skeletal anomalies in addition to variable malformations in the hindbrain, heart, intestines, and kidneys that frequently lead to perinatal death. The most severe phenotype, MNS, is characterized by a skeletal dysplasia in the heterozygote. Affected males exhibit severe malformations similar to those observed in individuals with OPD2, resulting in prenatal lethality or death in the first few months of life (review by Robertson, 2005). Verloes et al. (2000) suggested that these disorders constitute a single entity, which they termed 'frontootopalatodigital osteodysplasia.'
Fitch et al. (1976) described a male infant with microcephaly, small mouth, cleft palate, flexed overlapping fingers with syndactyly of digits 3 and 4, and syndactyly of toes 2 to 5. An earlier born half sib, who died at the age of 10 days, had the same features. Although the features suggested trisomy 18, karyotype was normal. The mother had a high-arched palate, bifid uvula, slight ulnar deviation of the terminal phalanges of the third fingers, radial deviation of the terminal phalanx of the right fourth finger, and slight clinodactyly of the fifth fingers. The half sibs had different fathers. The mother had a normal son and daughter. Similar cases were found in the literature among those reported as trisomy 18 phenotype with normal karyotype. Kozlowski et al. (1977) described 2 half brothers (with the same mother) who may have had the same disorder. Andre et al. (1981) described a family in which 3 male first cousins, sons of 3 sisters, had a phenotype almost identical to that in the patients described by Fitch et al. (1976). The sisters, 2 of whom had the same father, had minor anomalies typical of OPD I. Fitch et al. (1983) suggested that all these patients had the same disorder, presented a follow-up of their original patient, and pointed out similarities to OPD I. The follow-up radiographs on the Fitch patient (Fitch et al., 1983) showed extraordinary changes in the hands and feet: short great toe (short first ray) and relatively long second ray in the feet, abnormal epiphyses of the proximal phalanges of the hands, short first metacarpal, and extra bone in the capitate-hamate complex. The maternal grandmother had cleft palate. Fitch et al. (1983) suggested that the cranioorodigital syndrome be called OPD II and that it may be due to an allelic gene or even the same gene as OPD I.
Brewster et al. (1985) described a male infant and his maternal uncle, also an infant, with a lethal skeletal dysplasia characterized by cleft palate, midface hypoplasia, downward-slanting palpebral fissures, small thorax, and bowed limbs with absent fibulae. Heterozygous females are more mildly affected in this syndrome; the woman who was mother of 1 infant and sister of the other was 142 cm tall and had mild frontal bossing and downward-slanting palpebral fissures. Chondroosseous histology was normal.
Holder and Winter (1993) suggested that the disorder is X-linked semidominant: carrier females may exhibit mild dysmorphic features such as broad face, downslanting palpebral fissures, cleft palate, or bifid uvula (Andre et al., 1981). Radiologic features, such as hyperostosis of the skull bones, may also be present in carrier females.
Ogata et al. (1990) suggested that the clinical, radiologic, and histologic findings indicated that defective intramembranous ossification is a principal abnormality in OPD type II.
Stratton and Bluestone (1991) described a family in which an infant propositus had abnormalities that appeared to combine features of OPD II with those of the syndrome of hydrocephalus and cerebellar hypoplasia (307010); 2 maternal uncles died neonatally with congenital hydrocephalus and digital abnormalities consistent with OPD II. Stratton and Bluestone (1991) suggested that these 2 entities may be caused by mutations at neighboring loci on the X chromosome.
Young et al. (1993) described 3 cases of OPD II with omphalocele; 2 of the patients were brothers. In addition, the 3 males had other anomalies: hypospadias in 1, hydronephrosis in 2, hydroureter in 2, chordee in all 3, and hydrocephalus in 2. Young et al. (1993) pointed to reports of omphalocele in 3 other cases of OPD I or II.
Small or absent fibula and the presence of only 4 toes is typical of OPD II (Kozlowski, 1993).
Preis et al. (1994) reported the cases of 2 unrelated boys who showed growth retardation, bowed long bones, missing hypoplastic fibulas, sclerosis of the skull base, and wavy, irregular clavicles and ribs. The facial appearance was distinguished by a prominent forehead, widely spaced eyes, downslanting palpebral fissures, flattened nasal bridge, and retrogenia. One boy suffered a spontaneous fracture of one rib at the age of 3 years 5 months. The mother of the other affected boy had a large skull with prominent forehead, hypertelorism, low-set ears, high-arched palate, and retrogenia. She had a persistent deciduous incisor in the left maxilla, and several permanent teeth were missing due to agenesis or extraction. In addition, she had hearing loss and mild flexion contracture of the right elbow. On radiologic examination, the maxillary sinuses were absent, and the bone density of the skull bones and long bones was increased. In the opinion of Preis et al. (1994), the mother was mildly affected by the same condition. They found reports of 20 fully affected patients and 9 partially affected mothers, including their patient.
Stoll and Alembik (1994) reported a sporadic case of OPD II. At 26 years of age, the patient had conductive hearing impairment, cleft palate, prominent forehead, flat facies, and a broad nasal base resulting in the characteristic 'pugilist' appearance. Extension and supination were limited at the elbows; thumbs and halluces were broad. Radiologic abnormalities noted included malformations of the cervical spine, pelvic abnormalities, bilateral coxa valga, genu valgum, small fibulae, pes equinovarus, and supernumerary carpal bones. IQ had been measured as 65 at the age of 3 years when operation for pes equinovarus was performed. Bilateral conductive hearing loss was noted at the age of 6 years and malformed ossicles were seen at surgery at age 13 years. At the age of 27 years, IQ was measured as 95. He had been fitted with hearing aids since the age of 13.
Nishimura et al. (1997) described 2 males with many manifestations suggestive of OPD2; however, atypical skeletal changes cause some diagnostic confusion with lethal or semilethal bone dysplasias, including boomerang dysplasia (112310), type I atelosteogenesis (108720), type III atelosteogenesis (108721), and the lethal male phenotype of Melnick-Needles syndrome. The observations were thought to expand the entities that constitute the OPD-Larsen spectrum or family of skeletal dysplasias as postulated by Spranger (1985).
Savarirayan et al. (2000) reported 3 cases of OPD II emphasizing chondroosseous morphology. Although endochondral ossification was normal, periosteal ossification was defective with islands of cortical bone aplasia and hyperplasia of the periosteum. The trabecular bone was also very poorly formed and markedly hypercellular. Both membranous ossification and bone remodeling appear to be defective in OPD II and should account for part of the observed phenotype. Savarirayan et al. (2000) pointed out that the biglycan gene (BGN; 301870) maps to Xq28 and is involved in bone formation; however, they excluded BGN as a candidate by direct sequencing of cDNA in 1 case. Savarirayan et al. (2000) commented that their patient 1, who died shortly after birth due to severe pulmonary hypoplasia, had downslanting palpebral fissures and small mouth; the pelvic bones were deformed, the femurs and tibias were bowed, and the fibulas absent. The feet showed a 4-toed ('tree frog') configuration. The mother had hypertelorism and downslanting palpebral fissures. The mother and maternal grandfather of patient 2 had acromegaly, but this was probably unrelated to the OPD II. There was a family history of a 'maternal nephew' born with multiple malformations.
Verloes et al. (2000) reported a mild case of OPD2, a severe case of OPD2 with anomalies of the central nervous system and some manifestations of frontometaphyseal dysplasia, a lethal case of OPD2 with similarities to Melnick-Needles syndrome, and 3 unrelated boys born to mothers with MNS (1 with a severe form, 1 with a lethal form, and an aborted fetus). They reviewed the features in these disorders and in OPD1 and suggested that these disorders constitute a single entity. Verloes et al. (2000) also discussed the relationship to similar syndromes, such as Yunis-Varon syndrome (216340), type III atelosteogenesis (108721), and boomerang dysplasia (112310).
Morava et al. (2003) described 2 families in which both males and females showed the facial and skeletal characteristics of FMD in association with severe progressive scoliosis. Some also had hearing loss and urogenital anomalies, leading Morava et al. (2003) to suggest that these were examples of frontootopalatodigital osteodysplasia as described by Verloes et al. (2000).
Johnson et al. (2008) reported a brother and sister with a clinical diagnosis of OPD2 who both had tracheomalacia requiring tracheostomy to relieve lower airway obstruction.
OPD1 (311300) is an X-linked semidominant condition characterized by malformations of the skeleton, auditory apparatus, and palate. Linkage studies mapped the responsible gene to a 16-cM region of Xq27-q28. A proposed allelic variant of OPD1, termed OPD2, is associated with a more severe, frequently lethal phenotype with visceral and brain anomalies in addition to skeletal, auditory, and palatal defects. Robertson et al. (2001) reported linkage of the OPD2 phenotype to a 2-cM region of distal Xq28 in a Maori kindred, with a maximum multipoint lod score of 3.31 between the markers DXS1073 and DXS1108. This provided support for allelism between OPD1 and OPD2 and reduced the size of the disease interval to 1.8 to 2.1 Mb. They also demonstrated that female carriers of this disorder exhibit skewed inactivation that segregates with the high-risk haplotype and may be inversely related to the severity with which they manifest features of the disorder.
Robertson et al. (2003) demonstrated that OPD2 is caused by gain-of-function mutations in the gene encoding filamin A (FLNA; 300017). Loss-of-function mutations in FLNA result in an embryonic lethal state in males and manifest in females as a localized neuronal migration disorder, called periventricular nodular heterotopia (PVNH; 300049).
In a 12-year-old Japanese boy with OPD2, Kondoh et al. (2007) identified a mutation in the FLNA gene (R196W; 300017.0026). The patient had some additional unusual features, including congenital cataract, glaucoma, and congenital heart defects. Kondoh et al. (2007) noted that Robertson et al. (2003) had identified the same mutation in a patient with OPD type I, suggesting that additional factors play a role in OPD spectrum disorders.
In a male fetus with OPD2, Marino-Enriquez et al. (2007) identified a mutation in the FLNA gene (C210F; 300017.0027); analysis of relatives revealed that the mutation had arisen de novo in the mother. A previous pregnancy had ended in stillbirth of a male also diagnosed with OPD2, who on autopsy was noted to have deficiency of the lower thoracic, lumbar, and upper sacral vertebral arches. Histopathologic studies of the second fetus revealed osseous sclerosis rather than the previously reported membranous ossification defect observed in this condition.
In 6 females with cranial hyperostosis and various skeletal abnormalities from a 4-generation pedigree, Stefanova et al. (2005) identified heterozygosity for a deletion in the FLNA gene (300017.0016). The phenotype of affected females resembled FMD with some overlap to OPD1 and OPD2, but no signs specific for MNS. However, males had severe extraskeletal malformations and died early, thus constituting an overlap with OPD2 and MNS. Stefanova et al. (2005) concluded that the disorder in this family is best described as an intermediate OPD-spectrum phenotype that bridges the FMD and OPD2 phenotypes.
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