Isolated late-onset cone-rod dystrophy revealing a familial neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome with the T8993G mitochondrial mutation

PURPOSE: To report a late-onset cone-rod dystrophy that revealed a familial neurogenic muscle weakness, ataxia, and retinitis pigmentosa syndrome as a consequence of the T8993G mitochondrial mutation. METHODS: Observational case series. A 42-year-old fe, male disclosed a late ,onset retinal dystrophy. The family history revealed that her three sons, one of them de, ceased at the age of 4, had mental and neurologic impairmen t of variable severity. The retinal dystrophy of the mother was classified as a cone,rod dystrophy. Retinal dystrophy was subsequently diagnosed in th e two surviving sons. Screening for mutation in the mitochondrial DNA (mtDN A) was performed because of the combination of neurologic involvement and r etinal dystrophy in this family. RESULTS: Molecular analysis of the mtDNA revealed the ATPase-6 gene T8993G mutation in the mother and the two sons. CONCLUSION: This family illustrates the remarkably variable expression of r etinal and systemic manifestations related to the T8993G mutation ranging f rom an isolated late,onset cone,rod dystrophy to a severe neurodegenerative process with a dramatic outcome. Genetic counseling for retinal dystrophie s requires careful evaluation of the familial medical history.