Myoclonic epilepsy with red ragged fibers (MERRF)
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Myoclonic epilepsy with red ragged fibers (MERRF) is a rare, multisystem mitochondrial disorder.
Patients usually present in late adolescence or early adulthood with 1-3
- 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 3.
The mitochondrial gene MT-TK, which encodes tRNALys, is the most commonly affected with an A-to-G transition at nucleotide 8344 (80%) 3.
- serum and CSF lactic acidosis
- high CSF protein
Neuroradiological features of MERRF can be seen on CT and/or MRI 1,2:
- 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
- 1. Ito S, Shirai W, Asahina M et-al. Clinical and brain MR imaging features focusing on the brain stem and cerebellum in patients with myoclonic epilepsy with ragged-red fibers due to mitochondrial A8344G mutation. AJNR Am J Neuroradiol. 2008;29 (2): 392-5. doi:10.3174/ajnr.A0865 - Pubmed citation
- 2. Diagnostic Radiology: Paediatric Imaging. Jp Medical Ltd. ISBN:9350252058. Read it at Google Books - Find it at Amazon
- 3. DiMauro S, Hirano M. MERRF. 2003 Jun 3 [Updated 2015 Jan 29]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2015. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1520/