Abstract
MERRF (Myoclonus. Epilepsy Ragged Red Fiber) syndrome is one of well characterized mitochondrial encephalomyopathy with maternal inheritance due to a heteroplasmic A-to-G poml mutation at bp 8344 in mtDNA, in the gene coding for tRNALYS, in majonly of cases (<80%). At present, no effective treatment is available for this progressive disabling neuromuscular disease with identification of mitochondrial mutation, therefore the development of effective genetic counseling is very much in need for the pt and family with the mutation. Yet the nature of heteroplasmy of mitochondrial mutation make the genetic counseling limited value with difficulty in predicting clinical phenotypc we have mdentified mt mutation of tRNALYS in a 31 yo single female with clinical Dx. of MERFF syndrome and in her 4 other family members : a 29 y.o married sister with mild myoclonus without epilepsy who wants to start family, a 34 y o uneffected sister who is seeking genetic counseling for her two normal children. Mithochondiral mutation was determined by RFLP of PCR DNA product with mismatched primer following Nae I restriction enzyme digestion of Genomic DNA from PB. The mutation load (Ratio of mutant DNA/nl DNA) was found to be variable in the family. 60% in the proband, 80% in mildly affected sister and 50% in unaffected sister with 80% in a 7 y o her daughter and 60% in a 10 y o her son Therefore no positive relationship between mutation load in PB and clinical phenotype was found nor mutation load in the mother and phenotype of offspring can be predicted in this family The genetic counseling for prenatal and presymptomatic DX may offer onlv limited value for the family
Further studv including mutation load in muscle biopsy along with prospective-follow up study of the family may provide additional Data which can be informative in genetic counseling
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Kim, H., Park, S., Ha, M. et al. Identification of mitochondria) mutation (tRNAlys) & genetic counseling in a family with MERRF syndrome. Genet Med 2, 80 (2000). https://doi.org/10.1097/00125817-200001000-00102
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DOI: https://doi.org/10.1097/00125817-200001000-00102