Myoclonic Epilepsy with Ragged Red Fibers (MERRF) is a rare systemic disorder associated with mutations in mitochondrial DNA (mtDNA).


Genes affected: mitochondrial DNA (MT-TK, MT-TF, MT-TL1, MT-TP)


Key clinical features of MERRF:

(1) myoclonus

(2) generalized epilepsy

(3) ataxia

(4) ragged-red fibers in a muscle biopsy


Additional clinical findings may include:

(1) sensorineural hearing loss

(2) myopathy

(3) peripheral neuropathy

(4) short stature

(5) dementia

(6) optic atrophy and/or ophthalmoparesis

(7) exercise intolerance

(8) cardiomyopathy with Wolff-Parkinson-White (WPW) syndrome

(9) pigmentary retinopathy

(10) pyramidal signs

(11) lipomatosis (multiple lipomas)

(12) respiratory insufficiency


Laboratory confirmation involves demonstration of a mitochondrial DNA pathologenic variant.


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