GENOTYPE-PHENOTYPE CORRELATION IN ADULT-ONSET ACID MALTASE DEFICIENCY

We performed a clinical, biochemical, and genetic study in 16 patients from 11 families with adult-onset acid maltase deficiency. All patien ts were compound heterozygotes and carried the IVS1(-13T-->G) transver sion on one allele; the second allele harbored either a deletion of a T at position 525 in exon 2 (7 probands, 64%) or a deletion of exon 18 (1 proband, 9%). Deterioration of handicap was related to age, and de crease in vital capacity to duration of the symptomatic stage. Respira tory insufficiency was never the first manifestation. The levels of ac tivity of serum creatine kinase and of alpha-glucosidase in peripheral blood cells or muscle were helpful for the diagnosis, but did not hav e prognostic value. The adult form of acid maltase deficiency appears to be both clinically and genetically rather homogeneous; decrease of alpha-glucosidase activity is the final common pathway leading to dest ruction of muscle fibers and progression of muscle weakness over a per iod of years.