Deafness, X-Linked 7

A number sign (#) is used with this entry because of evidence that X-linked deafness-7 (DFNX7) is caused by hemizygous mutation in the GPRASP2 gene (300969) on chromosome Xq26. One such family has been reported.

Description

DFNX7 is a congenital form of bilateral mixed or conductive hearing loss, which may be progressive. It is not associated with vestibular symptoms (Xing et al., 2017).

Clinical Features

Xing et al. (2017) reported a 5-generation Chinese family in which 6 males had congenital bilateral hearing loss. The proband (V-4) exhibited symmetric and conductive hearing loss, whereas the 3 other affected men who were examined (IV-9, III-6, III-13) had mixed hearing loss. All had ear anomalies, including canal atresia in 4 and abnormal auricular shape and inner ear malformations in 3. Hearing loss was described as progressive in 3 and as nonprogressive in 1. None of the patients complained of vestibular symptoms. All of the patients had facial dysmorphism, including telecanthus in 4 and bilateral ptosis, heavy eyebrows, and broad nasal root in 3. None had developmental delay or intellectual disability.

Molecular Genetics

In affected male members of a Chinese family with congenital hearing loss, Xing et al. (2017) identified a hemizygous mutation in the GPRASP2 gene (A573N; 300969.0001) that segregated with hearing loss in the family. The mutation, which was found by whole-exome sequencing and confirmed by Sanger sequencing, was not found in 300 ethnically matched controls. No functional studies were performed.