Severe Haemolytic Disease in an Infant Born to an Rhnull Proposita

A 35-year-old Brazilian woman (gravida 4, para 2) was delivered of a severely anaemic child whose cord red blood cells had a strongly positive direct antiglobulin test and who required two exchange transfusions within 24 h of birth. Because of the emergency of the situation and the lack of a local immunohaematology reference laboratory, the phenotype of the mother and the specificity of the relevant antibody could not be determined. Hence, compatible blood was not immediately available and the infant had to be given repeated exchange transfusions with incompatible group 0 Rh-negative blood. The infant is now healthy and thriving. The mother's red cells were subsequently found to lack all the antigens of the Rh system, and her serum reacted with all red cell samples except those of two unrelated Rhnull individuals. Her serum gave high titres (i.e. 1,024–4,096) by the indirect antiglobulin test against red cells of normal Rh phenotype, as well as against cells with partially deleted Rh phenotypes (titres = 128–512 with –D–·/–D– and ·D·/·D· samples, respectively), and was extremely active in antibody-dependent cell-mediated cytotoxicity and monocyte monolayer assays against red cells of normal Rh phenotypes.