Résumé :
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Communication n° 378. Mitochondrial DNA (mtDNA) deletions are associated with three main phenotypes with very different severity. Two of them are severe multisystemic disorders (Pearson, Kearns-Shy Sayre (KSS) syndromes), and one is much milder involving mostly or only muscle (Chronic Progressive External Ophtalmoplegia (CPEO)). This clinical classification is also blurred by numerous overlapping cases: for example CPEO+ patients or patients with incomplete KSS. Potential evolution is therefore an essential issue when first establishing the diagnosis of mtDNA deletion. However severity and clinical evolution of the patient is considered at present unpredictable. We addressed this issue by the retrospective analysis of 78 patients with mtDNA deletion in muscle. Age at onset and evolution of each symptom was noted in the attempt to find clinical clues allowing to predict future evolution of the patient. Furthermore, in order to look for a relationship between clinical phenotype and site, size or amount of deletion, we identified, for each patient, the borders of the deletion and evaluated the amount in muscle of deleted and wild type mtDNA using real time PCR. Lastly, in order to look for an impact of the tissue distribution of the deletion, we looked, in 28 patients with available samples, for the presence of the deletion in non muscle tissues such as leucocytes, urine, or buccal cells.
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