Atypical presentation of acute phase, antibody-induced haemolytic anaemia in an infant

We describe a case of 'warm' antibody-induced haemolytic anaemia (WAIHA) in which marked depression of red cell Rh antigen expression resulted in the patient presenting with severe anaemia but a negative direct antiglobulin test (DAT). The serum contained potent IgG Rh antibodies. Unlike two previously reported cases (Koscielak, 1980; Veer et al. 1981) in which the diagnosis of WAIHA was established before the DAT became negative, this patient presented with negative serological findings during his first episode of anaemia. As a result, the serum antibodies appeared to be allo- not autoimmune in nature and to be unrelated to the patient's anaemia. Confirmation of the autoimmune nature of the Rh antibodies was not possible until nearly 2 years after the first episode of anaemia.