Clinical variability in adult-onset acid maltase deficiency: report of affected sibs and review of the literature.

Acid maltase deficiency (AMD) is a rare cause of muscle disease in adult patients. The present report of 2 sibs and review of 36 previously reported cases illustrates the vast clinical variability in adult-onset AMD. This is 1 of only 3 reports to document tongue weakness and enlargement in an adult with AMD. The presenting signs and symptoms usually include progressive limb weakness, restrictive lung disease, or both. Consistent supportive abnormalities include a modest elevation in serum CK, a reduction in the forced vital capacity, and abnormal spontaneous activity (that is, myotonic discharges or fibrillations) in resting muscles during needle electromyography. The clinical spectrum is also extended to include distal limb weakness, scapular winging, asymmetric muscle weakness, and tongue involvement.