Molecular Genetics
Mitochondrial Studies: MERRF – Myoclonus Epilepsy Associated with Ragged-Red Fibers
Background:
Myoclonic epilepsy with ragged-red fibers (MERRF) is a disorder that affects many parts of the body, particularly muscles and the nervous system. Usually the signs and symptoms of this disorder appear during childhood or adolescence. The features of MERRF vary widely among affected individuals, even among members of the same family.
The MERRF assay is clinically indicated for the evaluation of patients with the following clinical criteria (GeneTests Reviews):
- Myoclonus
- Generalized epilepsy
- Ataxia
- Ragged-red fibers (RRF) in the muscle biopsy
MERRF is associated with an A to G point mutation at nucleotide 8344 in the mitochondria tRNALys gene. This mutation is responsible for approximately 80% of MERRF cases. A small proportion of cases are caused by a T to C point mutation at nucleotide 8356 in the same gene.
Reason for Referral:
- Diagnostic Testing
- Prenatal Diagnosis
Methodology:
The two point mutations described above are detectable by PCR and restriction enzyme based analysis.
Specimen Requirements:
- Muscle: 50 mg muscle
- Blood: 6.0 mL EDTA (purple-top) or ACD (yellow-top) tube
- DNA: 10µg at a minimum of 100ng/µL
A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES. Please include detailed clinical information, including ethnicity, clinical history, and family history.
Test Performed (Days):
Weekly
Turn Around Time:
14 – 21 Days
Shipment Sensitivity Requirements:
- Package and ship specimen to remain cold, but not frozen.
- Ship via overnight express, using the FedEx priority overnight label provided.
- Contact Client Services for shipping kits and instructions at (855) 535-1522.
References:
1. DiMauro, S and Hirano, M. MERFF. Myoclonic Epilepsy Associated with Ragged Red Fibers. Gene Reviews [Internet]. http://www.ncbi.nlm.nih.gov/books/NBK1520/.
Additional Info:
This test detects point mutations that are present in levels greater than or equal to approximately 5% of total mtDNA.