Detection of neutrophil-associated immunoglobulin using flow cytometry in autoimmune neutropenia of infancy

Background : Autoimmune neutropenia of infancy (ANI) is a common form of chronic childhood neutropenia, which is caused by antineutrophil antibodies. The syndrome is characterized by a severe selective neutropenia accompanied with recurrent bacterial infections. Methods : We investigated 10 ANI patients in our hospital. Neutropenia in ANI patients was found in patients aged between 9 and 19 months. They had no life‐threatening infections and their infections episode could be controlled by the conventional antibiotic therapy in general. The correlation of absolute neutrophil counts (ANC) and neutrophil‐associated immunoglobulin (NAIg) levels in each case was analyzed and their clinical courses followed. Results : The NAIg levels were high in all cases at the diagnosis, however, they had no relationship with ANC. The severity of infection and the period of neutropenia in our patients have no correlation to NAIg levels either. In our four cases, neutropenia disappeared after a median of 26 months (range, 18−29 months). The periods of neutropenia were nearly similar to previous reports. After the NAIg level began to wane, neutrophil counts increased in four patients whose neutrophil counts had recovered finally. Conclusions : Detection of NAIg is useful for the diagnosis, and the observation of changes in NAIg may be helpful one by one for prediction of the prognosis.