AMP deaminase deficiency in skeletal muscle is unlikely to be of clinical relevance.

BACKGROUND: The homozygous c.34C>T mutation in the AMPD1 gene encoding the muscle-specific isoform of AMP deaminase (AMPD) accounts for the vast majority of inherited skeletal muscle AMPD deficiencies. It is controversial (i) whether AMPD deficiency is associated with exercise-induced complaints and (ii) whether an acquired form exists in which an underlying neuromuscular disorder additionally lowers the AMPD activity.
DESIGN: c.34C>T mutation (homozygous- TT, heterozygous-CT,wildtype-CC) was screened in 107 healthy blood donors and 294 patients with skeletal muscle biopsy including 200 with exercise-induced complaints. Additional screening for c.468G > T and c.860A > T mutations was performed in all CT.AMPD was analysed histochemically and biochemically.
RESULTS: The mutant allele frequency (MAF) was not different in blood donors, patients with muscle biopsy, and the subgroup with exercise-induced complaints (12.9-16.8 %). CT was found in 63 and TT in 13 patients. The c.468G>T mutation was not detected. The c.860A > T mutation was found in 2.8 % blood donors and 1.6% CT. AMPD activities showed a substantial overlap in CC and CT, but not with TT. AMPD activities in TT, CT, and CC did not differ in patients with a defined neuromuscular disorder and those with only exercise-induced complaints. In TT, CT, and CC there were no differences in the frequency of signs and symptoms, hyperCKemia, or myopathological biopsy pattern.
CONCLUSION: MAF did not differ in normal and diseased populations. The frequency of exertion-induced complaints was not higher in TT than CC. There was no specific phenotype of TT and no evidence for an acquired form of AMPD deficiency.