Myoclonic epilepsy with red ragged fibers (MERRF)

Myoclonic epilepsy with red ragged fibers (MERRF) is a rare, multisystem mitochondrial disorder.

Clinical presentation

Patients usually present in late adolescence or early adulthood with

• myoclonus
• epilepsy
• cerebellar ataxia
• intellectual disability
• vision and/or hearing loss
• cardiomyopathy with Wolff-Parkinson-White syndrome
• short stature

Pathology

The diagnosis of MERRF is based on clinical symptoms (myoclonus, epilepsy, ataxia) and ragged-red fibers on muscle biopsy .

Genetics

The mitochondrial gene MT-TK, which encodes tRNA, is the most commonly affected with an A-to-G transition at nucleotide 8344 (80%) .

Markers

• serum and CSF lactic acidosis
• high CSF protein

Radiographic features

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

Differential diagnosis

On imaging consider:

• MELAS: differentiated by the presence of strokes in MELAS