Auto-anti-Jka in Evans' syndrome with negative direct antiglobulin test.

A patient presented with haemolytic anaemia and a negative direct antiglobulin test (DAT), and was found to have an IgG antibody with anti-Jka specificity in his serum. His red cells were typed as Jk(a-b+). Later he developed idiopathic thrombocytopenic purpura (ITP), and had a positive DAT due to anti-Jka bound to his red cells, which now typed as Jk(a+b+). Family studies suggested that the patient's true type was Jk(a+b+). Splenectomy and immunosuppression were required to treat the thrombocytopenia. The autoanti-Jka was no longer detectable following therapy.