AMPD1 and myopathy: AMPD1 is very strongly expressed in skeletal muscle and diaphragm (Morisaki et al., 1990), and it has been examined extensively for the impact of a non-sense mutation that is common in European ancestry populations but rare in most other world-wide population samples (rs17602729; Gln45Ter; C34T; AFT-EUR = 0.123 in 1000 Genomes)5 Originally, deficiency in AMPD1 due to rs17602729 homozygosity (TT) was identified as a putative cause of myopathy (Fishbein et al., 1978).