ClinVar

In a male patient with pigmentary retinopathy with visual loss, bilateral sensorineural deafness, muscle hypotrophy, testicular dysfunction, and ataxia, Crimi et al. (2003) identified a heteroplasmic 12183G-A mutation in the MTTH gene. The mutation occurred in a highly conserved region of the T-psi-C stem of the tRNA. The clinical course was progressive, with visual loss beginning at age 7 years, hearing loss at age 11 years, and muscle weakness, ataxia, dysarthria, and testicular dysfunction apparent by age 20 years. Brain imaging showed cerebellar hypotrophy and bilateral basal ganglia calcifications. The patient's sister had retinopathy and sensorineural hypoacusis, whereas their mother had bilateral cataracts and audiometric defects; both also carried the 12183G-A mutation. Crimi et al. (2003) noted that the gradient of clinical severity reflected the degree of mutation heteroplasmy.