<unk>  (ADA deficiency) is a metabolic disorder that causes immunodeficiency. It is caused by mutations in the ADA gene. It accounts for about 10–15% of all cases of autosomal recessive forms of severe combined immunodeficiency (SCID) among non-inbred populations. ADA deficiency can present in infancy, childhood, adolescence, or adulthood. Age of onset and severity is related to some 29 known genotypes associated with the disorder. It occurs in fewer than one in 100,000 live births worldwide.
Adenosine deaminase deficiency
Adenosine deaminase 2 deficiency
Adenine phosphoribosyltransferase deficiency
Guanidinoacetate methyltransferase deficiency
Galactose-1-phosphate uridylyltransferase deficiency
Methylenetetrahydrofolate reductase deficiency
Mevalonate kinase deficiency
Adenosine monophosphate deaminase deficiency type 1