Résumé :
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We describe the case of a young algerian patient, now 27 years old, whose parents are cousins and one of his 5 brothers died suddenly during an effort at the age of 18 years. From age of 7 years, he complains of muscle fatigability, nausea and often feels faint favoured by stress and exercise. He presents with a moderate girdle weakness and diffuse hypotrophy. CK are normal, as glucose tolerance test. Glucagon test produced a normal increase of the glycemia, suggesting a normal hepatic glycogen storage. EMG is myopathic without myotonia. PAS reagent and electron microscopy of two muscles biopsies performed in 1997 and 2002 revealed vacuolar myopathy with absence of intrasarcoplasmic glycogen. Quantitative muscle glycogen was low. Exercise tests showed limited lactate increase, poor performance but the test was stopped as a faint occurred. Cardiac evaluation showed a mild left ventricular hypertrophy, numerous atrial extrasystoles on 24-hour recording of cardiac rhythm. The heart muscle biopsy failed as it induced a serious faint. This case is a new one of muscle glycogen storage disease so-called type 0, recently described in three siblings by Kollberg et al (2007). The risk of cardiomyopathy with sudden death probably responsible for his brother’s death is high, and justify cardiac monitoring and prevention of stress. A defibrillator implantation is debated. We identified a homozygous c.678+1G>A splicing mutation in the GYS2 gene coding for the muscle isoform of the glycogen synthase. The mutation led to an in-frame exon 4 skipping and to a strong instability of the deleted transcript. Western-blot analysis confirmed the absence of the muscle glycogen synthase isoform. Both parents were carriers for the mutation.
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