Severe congenital neutropenia (SCN), also often known as Kostmann syndrome or disease, is a group of rare disorders that affect myelopoiesis, causing a congenital form of neutropenia, usually without other physical malformations. SCN manifests in infancy with life-threatening bacterial infections. Kostmann disease (SCN3), the initial subtype recognized, was clinically described in 1956. This type has an autosomal recessive inheritance pattern, whereas the most common subtype, SCN1, shows autosomal dominant inheritance.