EXERCISE INTOLERANCE AND RECURRENT MYOGLOBINURIA AS THE ONLY EXPRESSION OF XP21 BECKER TYPE MUSCULAR-DYSTROPHY

A 9-year-old boy complained of exertional myalgias and described two e pisodes of myoglobinuria. His family history was negative for neuromus cular diseases. The findings of a neurological examination were normal . Serum creatine kinase was increased, ECG was normal, EMG showed slig ht ''myopathic'' signs. Muscle biopsy disclosed a small group of basop hilic fibres as the only abnormality. Muscle glycolytic enzymes and ca rnitine palmitoyl transferase were normal. Immunoblotting using antidy strophin antibody demonstrated a protein with low molecular weight. Ge nomic DNA analysis showed a deletion of the HindIII fragments spanning from exon 45 to exon 48. Eight years after the first observation the patient has diffuse muscle hypertrophy without muscle weakness.