title: Severe megaloblastic anaemia associated with abnormal azathioprine metabolism.
abstract: Severe anaemia is a rare, unexplained, side effect of azathioprine therapy. We report here such a case associated with a previously unreported abnormality in azathioprine metabolism. A 57 year old man on azathioprine therapy, for a presumed collagen vascular disease, developed severe megaloblastic anaemia. This resolved on cessation of azathioprine treatment. A very high concentration of an azathioprine metabolite, 6-thioguanine nucleotide, was found in the patient's red blood cells and this was confirmed by subsequent rechallenge with a single dose of 50 mg azathioprine.
mesh_terms: D000748:Anemia, Macrocytic / Q000139:chemically induced*; D000749:Anemia, Megaloblastic / Q000139:chemically induced*; D001379:Azathioprine / Q000009:adverse effects*; D006150:Guanine Nucleotides / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D013873:Thionucleotides / Q000097:blood
chemical_list: D006150:Guanine Nucleotides; D013873:Thionucleotides; C003964:6-thioguanylic acid; D001379:Azathioprine