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[A8344G mitochondrial DNA mutation observed in two generations].

This article presents the case of a 62-year-old mother and her 41-year-old daughter, who have had severe neurological symptoms for a few decades. After a long investigation period the definite diagnosis of MERRF syndrome was confirmed. After DNA isolation from our patient's blood sample we examined the mitochondrial DNA with direct sequencing. An adenine-guanine substitution was detected in the tRNA gene at position 8344, based on the sequence ferogram the heteroplasmy was over 90%. The clinical phenotype was not clearly characteristic for MERRF syndrome, adult-onset and lipomas are not typical in this disease. In our case report we would like to draw attention to the great phenotypic variation of the mitochondrial diseases and we emphasize that these disorders are underdiagnosed in Hungary even today. Orv. Hetil., 2017, 158(12), 468-471.