An unusual Donath-Landsteiner antibody detectable at 37 degrees C by the antiglobulin test

A 14-year-old boy with no history of transfusion experienced a hemolytic crisis attributed to paroxysmal cold hemoglobinuria. The Donath-Landsteiner test was positive. The IgG autoantibody had anti-P specificity but was unique in that it also reacted strongly by indirect antiglobulin test at 37 degrees C.