DIAGNOSIS OF MCARDLES-DISEASE BY MOLECULAR-GENETIC ANALYSIS OF BLOOD

We analyzed leukocyte DNA from 32 patients with suspected McArdle's di sease, 24 of whom had biochemically or histochemically proven myophosp horylase deficiency. We found that 19 were homozygous for the most com mon mutation at codon 49, 2 were compound heterozygotes, and 1 was a m anifesting heterozygote. In six patients, we could find only one mutan t allele, suggesting a still unidentified mutation on the second allel e. We were unable to identify any of the known mutations in four patie nts. Our findings indicate that the diagnosis of McArdle's disease can be established in approximately 90% of patients using DNA isolated fr om leukocytes, thereby avoiding muscle biopsy.