pediatrics
Mitochondrial Oxidative Phosphorylation Disorders
Myoclonic epilepsy with ragged red fibers (MERRF)
This progressive disorder is characterized by uncontrolled muscle contractions (myoclonic seizures), dementia, ataxia, and myopathy, which shows ragged-red fibers (indicating mitochondrial proliferation) with specialized stains when biopsied. Mutations are in the mitochondrialtRNAlysgene. Heteroplasmy is common; thus, expression is variable. 