chromosome 1q21.2. Unlike classical Kostmann disease, SCN5 also has defective platelet aggregation (thrombasthenia) and myelofibrosis. This type is refractory to granulocyte colony-stimulating factor. There is an absence of lysosomes in fibroblasts and depletion of alpha granules in platelets. Accelerated apoptosis occurs in the neutrophils and bone marrow. X-linked SCN (SCNX) is caused by mutation in the WASP gene on Xp11. SCN occasionally may arise from SBDS mutations. Usage Severe congenital neutropenia (SCN) is used as the overarching term for all diseases that affect myelopoiesis most prominently. Kostmann syndrome can restrictively refer to Kostmann disease specifically, or can be used synonymously with SCN as an umbrella term. These syndrome subtypes are phenotypically similar despite arising from different gene abnormalities. Kostmann disease is a form of severe congenital neutropenia (SCN), specifically type 3 (SCN3), which is a rare autosomal recessive condition in which severe chronic neutropenia is detected soon after birth. The disorder was discovered in 1956 in an extended family in northern Sweden by Rolf Kostmann, a Swedish doctor. Although mutations of more than 15 genes cause severe congenital neutropenia (in a general sense) not all of these are usually considered as SCN. Clinical usage excludes two broad categories of congenital neutropenia. Diseases are excluded that overtly affect multiple systems rather than impacting myelopoiesis most prominently. Thus SCN excludes the severe neutropenia which can occur in congenital diseases such as Shwachman–Diamond syndrome, Barth syndrome, Chédiak–Higashi syndrome, WHIM syndrome, and glycogen storage disease type Ib. A further group of other miscellaneous inherited disorders, such as hyper IgM syndrome, Hermansky–Pudlak syndrome (HPS), Griscelli syndrome (GS), PN, P14 deficiency, Cohen syndrome, Charcot–Marie–Tooth disease (CMT) can show congenital neutropenia, but lack bone marrow findings typical of SCN. This group of diseases may also have additional features such as partial albinism, retinopathy, or neuropathy, and are not inclined to degenerate into acute myelogenous leukemia. GATA2 deficiency GATA2 deficiency is a grouping of several disorders caused by common defect, viz., familial or sporadic inactivating mutations in one of the two parental GATA2 genes. These autosomal dominant mutations cause a reduction, i.e. a haploinsufficiency, in the cellular levels of the gene's product, GATA2. The GATA2 protein is a transcription factor critical for the embryonic development, maintenance, and functionality of blood-forming, lympathic-forming, and other tissue-forming stem cells. In consequence of these mutations, cellular levels of GATA2 are deficient and individuals develop over time hematological, immunological, lymphatic, or other presentations