Sabinas Brittle Hair Syndrome

Description

The principal features of Sabinas brittle hair syndrome, a form of nonphotosensitive trichothiodystrophy (TTDN; see 234050), include congenital hypotrichosis, mild to moderate onychodysplasia, varying mental retardation, and sterility. Ocular dysplasias are sometimes present and dentition is normal (Howell et al., 1980).

Clinical Features

Arbisser et al. (1976) observed dry, brittle, fragile hair and mental deficit in a brother-sister pair from a small remote village of northern Mexico. The hair showed decreased cuticular layer and an apparently collapsed cortex. Other children in the village seemed to be identically affected but had not yet been studied. Further information was reported by Howell et al. (1980), who referred to the disorder as the Sabinas brittle hair syndrome after the name of the town of origin of affected families. Onychodystrophy was present in some. Affected persons could be identified from the newborn period by persistent scalp hypotrichosis. Postpubertal patients showed almost no axillary or pubic hair.

Howell et al. (1981) reported that the cystine content of hair was reduced, whereas the copper-zinc ratio in hair was increased. They had observed 12 patients in 5 seemingly unrelated families.

King et al. (1984) suggested that this disorder is the same as those described elsewhere as the Pollitt syndrome and the Amish hair-brain syndrome (see 234050).

Inheritance

Parental consanguinity and the occurrence of Sabinas syndrome in affected brothers and sisters support autosomal recessive inheritance (Howell et al., 1981).

Molecular Genetics

In 2 cases of Sabinas syndrome and 1 case of Pollitt syndrome, Nakabayashi et al. (2005) failed to find mutation in the C7ORF11 gene (609188), mutations in which were found in other nonphotosensitive TTD cases with mental retardation and decreased fertility (see 234050). The authors suggested that genetic heterogeneity in nonphotosensitive TTD is a feature similar to that observed in photosensitive TTD, which is caused by mutation in transcription factor TFIIH genes (see 601675).