Mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes: A distinctive clinical syndrome

TLDR

MELAS is a maternally inherited mitochondrial disorder characterized by ragged red fibers indicating electron‑transport‑chain dysfunction, though its precise biochemical defects remain unclear. The authors propose that MELAS constitutes a distinct clinical syndrome that can be differentiated from Kearns‑Sayre syndrome and myoclonus epilepsy ragged‑red‑fiber syndrome. In this series of eleven patients, MELAS manifested with ragged red fibers, normal early development, short stature, seizures, hemiparesis or visual loss, and frequent lactic acidosis.

Abstract

Abstract We report on two patients who have a mitochondrial myopathy, encephalopathy, lactic acidosis, and recurrent cerebral insults that resemble strokes (MELAS). These two and nine other reported patients share the following features: ragged red fibers evident on muscle biopsy, normal early development, short stature, seizures, and hemiparesis, hemianopia, or cortical blindness. Lactic acidemia is a common finding. We believe that MELAS represents a distinctive syndrome and that it can be differentiated from two other clinical disorders that also are associated with mitochondrial myopathy and cerebral disease: Kearns‐Sayre syndrome and the myoclonus epilepsy ragged red fiber syndrome. Existing information suggests that MELAS is transmitted by maternal inheritance. The ragged red fibers suggest an abnormality of the electron transport system, but the precise biochemical disorders in these three clinical syndromes remain to be elucidated.