McARDLE DISEASE: P.115 Natural history of McArdle disease in a cohort of 220 patients

Abstract

McArdle disease is caused by recessive mutations in the gene encoding muscle glycogen phosphorylase (MGP) which results in enzyme deficiency. The condition is considered to cause a 'pure' muscle phenotype with symptoms including: exercise intolerance, inability to perform isometric activities. Known associated complications include: hyperuricaemia and gout, acute rhabdomyolysis with myoglobinuria leading to compartment syndrome and acute renal failure. We retrospectively assessed case records of 220 patients with genetically confirmed McArdle disease from 2011-2019 and will report data relating to genotype, phenotype (including frequency of known associated complications) and functional capacity based upon a 12 minute walking test. We will also report results of prospective screening for other 'unexpected' co-morbidities in our cohort including the frequency of cardiovascular disease, thyroid disease and pattern retinal dystrophy. We also assessed the frequency of other systemic disorders. Our data suggest that MGP deficiency is not such a benign condition and may be associated with systemic issues beyond the skeletal muscles. The role of MGP in both skeletal and non-skeletal muscle tissues may give a clue as to the underlying pathogenesis of these co-morbidities. Prospective regular monitoring of these patients may be worthwhile.