Alloimmunisation in pregnancy is a very random event. We present a case of HDN caused by Anti-Wr(a). In transfused and pregnant patients this ab can be found in up to 1 of 50, and in 1 of 2-3 patients with autoimmunhemolytic anaemia. HDN and hemolytic transfusion reactions have been reported very rare. Mandatory antibody screening does not include Wr(a) positive cells. To our knowledge this is the first report in the German speaking area of HDN caused by Anti-Wr(a).

We used standard immuno-hematological techniques with direct anti globulin test (DAT), crossmatch, ab screening and -specification in BioRad antihuman globin (AHG) gel cards with test cells from BioRad and additional cells like Wr(a) positives (Sanquin). Typing was done serologically where possible. If impossible, we DNA-typed via rare ID SSP-PCR (inno train Diagnostics). Acid Elution (BAG) was done on the blood of the newborn.

A 34 y/o female (II. gravida I para) delivered in week 41 of pregnancy a jaundiced daughter. Signs of HDN with hemoglobin (Hb) 13.9g/dl, HCT 43%, red cells 3.32 Mio/µl, reticulocytes 18.93%, LDH 1965U/l, total bili 10.9mg/dl, ind. bili 9.67mg/dl were found. UV-treatment was successful. Symptomatic anemia (Hb 7g/dl) was transfused (Hb 13.1g/dl) on day 12.

Abroad routine ab screenings (abs) were negative throughout pregnancy and postnatally. Here, we found maternal Allo-Anti Wr(a), titre of 512. Fetal DAT was strongly positive. IgG subclasses hint high risk for hemolysis with low IgG1- and high IgG3-concentration. Father and baby were Wr(a) antigen (ag) positive. Ab in baby"s plasma and eluate proved maternal Anti-Wr(a) causal for HDN.

Whether testing for Anti-Wr(a) should be added as mandatory in the German prenatal care guidelines or whether this displays a neglectable singular case should be studied further. Still, Anti-Wr(a) should be considered and serologically excluded in any case of clinical HDN with positive DAT-results and negative abs.

No conflict of interest.