Kostmann disease with developmental delay in three patients.

Kostmann disease is a rare autosomal recessive form of severe congenital neutropenia characterized by maturation arrest at the stage of promyelocytes/myelocytes in bone marrow with peripheral blood absolute neutrophil counts below 0.5 x 10(9)/L and severe recurrent bacterial infections from early infancy. Kostmann disease is caused by homozygous mutations in the gene encoding the mitochondrial protein HCLS1-associated X1. Here, we report three patients with Kostmann disease who, besides recurrent infections, have developmental delay.