X-linked neutropenia (OMIM #300299) is an X-linked form of severe non-syndromic congenital neutropenia, caused by mutation in the WASP gene (OMIM ∗300392) mapped to the short arm of the X chromosome, Xp11.23.
X-linked neutropenia (XLN) is a rare severe congenital neutropenia (SCN) due to an activating mutation of WASP gene. As a result, the gene product Wiskott-Aldrich syndrome protein (WASP) is overactive. Mutations of the WASP gene are responsible for three distinct phenotypes: X-linked thrombocytopenia (XLT), classic Wiskott-Aldrich syndrome (WAS), and XLN. XLN is characterized by profound neutropenia, associated with monocytopenia and T lymphopenia, and an increased risk of myelodysplasia (MDS) and acute myeloid leukemia (AML). XLN is a rare cause of severe congenital neutropenias affecting about 2% of cases (Ochs 2009; Skokowa et al. 2017; Spoor et al. 2019).
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