The MELAS syndrome is a rare. neurodegenerative disorder associated with a mutation in mitochondrial DNA.


Location of defect: mitochondrial DNA (mtDNA) near nucleotide 3243

Effect: respiratory chain enzyme deficiency with defective oxidative phosphorylation


Inheritance: non-Mendelian, either sporadic or through maternal pedigree


Onset: typically under the age of 20


Key features:

(1) mitochondrial myopathy, with red ragged fibers on Gomori trichrome stain

(2) encephalopathy

(3) lactic acidosis

(4) stroke-like episodes in a non-vascular distribution (associated with microvascular damage)


CNS findings may include:

(1) seizures

(2) agitation

(3) hallucinations

(4) generalize asthenia

(5) migraine-like headaches

(6) cognitive dysfunction


Additional findings may include:

(1) diabetes mellitus

(2) hypothalamo-pituitary dysfunction

(3) focal segmental glomerulosclerosis

(4) ophthalmoplegia

(5) hypertrophic cardiomyopathy

(6) gastrointestinal dysmotility


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