Isoimmune neonatal neutropenia.

An unselected population of newborn infants at a tertiary perinatal center was the subject of an investigation of isoimmune neonatal neutropenia (INN) to determine the incidence of the disorder and further characterize its clinical and immunologic aspects. We screened 1465 consecutively born infants for neutropenia on the first day of life, and evaluated those with neutropenia for the presence of antineutrophil antibodies utilizing EDTA-microagglutination and indirect immunofluorescence. Of the 16 infants with persistent neutropenia, 3 were confirmed to have INN, representing 2/1000 live births and 1.5% of special care nursery admissions during the period. INN is not a rare disorder and should be considered in the evaluation of all infants with neutropenia, with or without infection. Our rapidly expanding knowledge of the neutrophil-specific antigen system is refining our ability to diagnose and treat immune neutropenias.