Alpha-sarcoglycan deficiency featuring exercise intolerance and myoglobinuria

Abstract

An 8-year-old boy was referred for recent onset of easy fatigue. He showed hyperCKemia and mild scapular winging. Muscle biopsy on the quadriceps muscle demonstrated slight fibre size variability. Dystrophin was normally distributed, carnitine palmitoyl transferase and glycolytic enzymes had normal activities. In the following years the patient developed exercise intolerance and myoglobinuria. Immunohistochemistry showed marked reduction of alpha-sarcoglycan, confirmed by Western blotting. Molecular analysis revealed compound heterozygosity with Arg284Cys and Glu137Lys substitutions, corresponding to nucleotide changes C850 T and G409 A in the gene. At present the patient, 20 years old, shows mild proximal weakness with prominent involvement of the paraspinal muscles, dorsal kyphosis and lumbar hyperlordosis. Exercise intolerance and myoglobinuria, already described in Becker muscular dystrophy, should be also considered among the possible presentations of sarcoglycan deficiencies.