Neonatal alloimmune neutropenia in premature monozygous twins

Alloimmune neonatal neutropenia (ANN) is an uncommon but potentially life-t hreatening disorder of the neonate and young infant. Hematologically, the m other's peripheral neutrophil count is normal. However, the passive transfe r of maternal immunoglobulin G neutrophil-specific antibodies and the subse quent sensitization of fetal neutrophils can result in severe neutropenia i n the neonate. Generally, ANN is a self-limiting condition, but with severe bacterial infection, mortality can be high. We present the clinical featur es of monozygous twins delivered at 33 weeks' postconception with this cond ition. This case report is unique in that it occurred in twins born prematu rely and was attributable to antibodies against 2 neutrophil-specific antig ens, NA1 and NB1. A brief review of the diagnosis, management, and treatmen t of ANN is presented.