Objective: To study the clinical, pathological and genetic characteristics of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS).
Methods: Eight cases of MELAS (6 of them were from 2 families) underwent clinical study, muscle biopsy, autopsy on one patient, brain biopsy on one patient and genetic research.
Results: In clinical report the average age of onset was 10-22 years old. Four cases from one family were 3 brothers and their nephew (sister's son). The death age of the three brothers was 16-20 years. Two cases from another family were a brother and a sister. The six patients of the two families showed the typical inherited characters of MELAS. The symptoms were myoclonic epilepsy, stroke-like episodes, paralysis of limbs, progressive mental retardation and neurological deaf. CT showed calcification in globus pallidus and MRI demonstrated clearly the abnormal prolongation of T2-weighed signals that distributed in frontal, parietal, occipital and temporal cortex as multiple focal, cystic and laminar necrotic areas. Pathological studies on brain showed multi-focal, cystic, and laminar or spongy necrotic abnormality primarily in gray matter of frontal, parental, temporal and occipital cortex. Decrease and loss of nerve fibers of the sub-cortical white matters of the lesion areas of cortex and calcification of globus pallidus were also observed. Red ragged fibers (RRF) and abnormal mitochondron were found by muscle biopsies. A point mutation (A-G transition) at nt 4243 in the mitochondrial tRNA Leu (UUR) was confirmed by using PCR and Southern Blot.
Conclusion: Although great progress has been made in the clinical, pathological and genetic research of MELAS, the pathogenesis of the disease remains further research.