MTTP and retinitis pigmentosa: To date, only 5 patients have been reported, each with different MT-TP mutations, and variable clinical features have been observed including ataxia, deafness, dilated cardiomyopathy, myoclonic epilepsy with ragged-red fibers–like disease, and retinitis pigmentosa; a myopathic phenotype is reported in all cases (table e-1).