EN
INTRODUCTION: Mitochondrial encephalomyopathies comprise a group of heterogeneous disorders which may result from mutations in mitochondrial (mtDNA) and nuclear genome (nDNA). From a variety of symptoms progressive external ophthalmoplegia (PEO) seems to be the most common. AIM(S): The aim of this study was the clinical and genetic characteristics of Polish patients with progressive external ophthalmoplegia. METHOD(S): Clinical, electrophysiological, neuroradiological and morphological data of 45 patients aged 11 to 76 years were analyzed. Genetic studies of mtDNA were performed in all patients. Among nDNA genes POLG was studied in 15 and C10orf2 in 6 patients. RESULTS: 16 patients with ptosis and PEO were included to chronic progressive external ophthalmoplegia (CPEO) group and 13 with ptosis, PEO and limb or trunk muscles’ weakness to CPEO+ group. There were 11 patients with PEO and the central nervous system impairment classified as mitochondrial encephalomyopathy (ME), 4 patients with Kearns-Sayre syndrome (KSS) and one patient with sensory ataxic neuropathy, dysarthria, ophthalmoparesis (SANDO) syndrome. Genetic studies of mtDNA revealed already known single or multiple mtDNA deletions in all patients and in most cases they were detected in the muscle tissue. Genetic analysis of nDNA genes confirmed mutations in POLG gene in 6 patients. There were 3 CPEO patients with p.[Arg309Leu];[Gln968Glu], p.[Ala518Thr];[=] and p.[Trp748Ser];[Ser998Pro] mutations, and 2 CPEO+ patients with p.[Thr251Ile;Pro587Leu];[Thr251Ile;Pro587Leu] and p.[Thr251Ile;Pro587Leu];[Lys1191Asn] mutations. In patient with SANDO syndrome the mutation p.[Arg290Cys];[Arg309Cys] in POLG gene was confirmed. Additionally the analysis of the C10orf2 gene proved the mutation p.[Arg374Gln];[=] in one CPEO patient CONCLUSIONS: Genetic studies of both mtDNA and nDNA are necessary for diagnosis of chronic progressive external ophthalmoplegia and its genetic counseling.