Adenosine monophosphate deaminase deficiency type 1

Adenosine monophosphate deaminase deficiency type 1 or AMPD1, is a human metabolic disorder in which the body consistently lacks the enzyme AMP deaminase, in sufficient quantities. This may result in exercise intolerance, muscle pain and muscle cramping. The disease was formerly known as myoadenylate deaminase deficiency (MADD).

In virtually all cases, the deficiency has been caused by an SNP mutation, known as rs17602729 or C34T. While it was initially regarded as a recessive (or purely homozygous) disorder, some researchers have reported the existence of similarly deleterious effects from the heterozygous form of the SNP. In the homozygous form of the mutation, a single genetic base (character) has been changed from cytosine ("C") to thymine ("T") on both strands of Chromosome 1 – in other words, "C;C" has been replaced by "T;T". A rarer but analogous condition, in which two guanine bases ("G;G") bases (in the unmutated form) have been changed to adenine ("A;A") has also been identified. While there has been no consensus on the effects of the heterozygous form – either "C;T" or "A;G" – some evidence has been found that it too has caused AMPD1 deficiency. In addition, some sources have suggested the existence of a rare, acquired form of AMPD1 deficiency.

AMPD1 deficiency is caused by a defect in the mechanism for production of AMP deaminase – an enzyme that converts adenosine monophosphate (AMP) to inosine monophosphate (IMP). While the deficiency affects approximately 1–2% of people in populations of predominantly European descent, the disorder appears to be considerably rarer in Asian populations.