Myoclonic epilepsy with red ragged fibers (MERRF)
Myoclonic epilepsy with red ragged fibers (MERRF) is a rare, multisystem mitochondrial disorder.
Patients usually present in late adolescence or early adulthood with
- cerebellar ataxia
- intellectual disability
- vision and/or hearing loss
- cardiomyopathy with Wolff-Parkinson-White syndrome
- short stature
The diagnosis of MERRF is based on clinical symptoms (myoclonus, epilepsy, ataxia) and ragged-red fibers on muscle biopsy .
The mitochondrial gene MT-TK, which encodes tRNA, is the most commonly affected with an A-to-G transition at nucleotide 8344 (80%) .
- serum and CSF lactic acidosis
- high CSF protein
Neuroradiological features of MERRF can be seen on CT and/or MRI :
- cerebral atrophy
- cerebellar atrophy
- high T2 white matter signal
- globus pallidal atrophy +/- calcification
- dentate nucleus calcification
On imaging consider:
- MELAS: differentiated by the presence of strokes in MELAS