MITOCHONDRIAL DNA DISORDERS
Mitochondrial DNA codes for mitochondrial oxidative phosphorylation enzymes;inheritance is only from mother to child, because only the ovum contributes mito-chondria to the zygote. Examples include:
· Leber hereditary optic neuropathy causes loss of retinal cells, which leads tocentral vision loss.
· Myoclonic epilepsy with ragged red fibers (MERRF) is a mitochondrial disor-der characterized by epilepsy, ataxia, peripheral neuropathy and deteriora-tion in cognitive ability. Sensorineural hearing loss and ocular dysfunction can also develop. Patients have short stature and cardiomyopathy. On muscle biopsy, ragged red fibers are seen on Gomori trichrome staining due to the accumulation of mitochondria.