pediatrics
Purine Catabolism Disorders
Myoadenylate deaminase deficiency (or muscle adenosine monophosphate deaminase deficiency)
The enzyme myoadenylate deaminase converts AMP to inosine and ammonia. Deficiency may be asymptomatic or it may cause exercise-induced myalgias or cramping; expression seems to be variable because, despite the high frequency of the mutant allele (10 to 14%), the frequency of the muscle phenotype is quite low in patients homozygous for the mutant allele. When symptomatic patients exercise, they do not accumulate ammonia or inosine monophosphate as do unaffected people; this is how the disorder is diagnosed. Treatment of myoadenylate deaminase deficiency is exercise modulation as appropriate. 