<unk>  or AMPD1, is a human metabolic disorder in which the body consistently lacks the enzyme AMP<unk> , in sufficient quantities. This may result in exercise intolerance, muscle pain and muscle cramping. The disease was formerly known as myoadenylate<unk>  deficiency. 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has been changed from cytosine ("C") to thymine ("T") on both strands of Chromosome 1 – in other words, "C;C" has been replaced by "T;T".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<unk>  – an enzyme that converts adenosine<unk>  (AMP) to inosine<unk>  (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.
Adenosine monophosphate deaminase deficiency type 1
Adenosine deaminase 2 deficiency
Adenosine deaminase deficiency
Galactose-1-phosphate uridylyltransferase deficiency
3-Methylcrotonyl-CoA carboxylase deficiency
Ornithine aminotransferase deficiency
Ribose-5-phosphate isomerase deficiency
Adenine phosphoribosyltransferase deficiency