Objective: To identify the disease-causing mutation in a large 3 generation pedigree of X-linked congenital nystagmus.
Methods: Twenty-three members of a single pedigree, including 7 affected males, 2 affected females, 5 obligate carriers, and 9 unaffected family members were tested for mutations in the FRMD7 gene using PCR-based DNA sequencing assays and multiplex PCR assays for deletions.
Results: A hemizygous deletion of exons 2, 3, and 4 of FRMD7 was detected in all affected males in the family and was absent from 40 control subjects.
Conclusions: A range of missense, nonsense, frameshift, and splicing mutations in FRMD7 have been shown to cause X-linked congenital nystagmus. Here we show for the first time that large intragenic deletions of FRMD7 can also cause this form of nystagmus.