Delayed hemolytic transfusion reaction caused by anti-Jsb in a Js(a+b+) patient

A 39-year-old multiparous woman developed a mixed field positive direct antiglobulin test within 15 days of receiving four units of crossmatch compatible red blood cells. Anti-Jsb was demonstrable in both the serum and the eluate. The case was further complicated by the fact that the patient's pretransfusion red blood cells typed as Js(b+). Serologic studies demonstrated that this was a case of allo-anti-Jsb in a Js(b+) patient which provides evidence of heterogeniety of the Js locus.