Autosomal dominant severe congenital neutropenia-9 (SCN9) is characterized by onset of neutropenia in the first years of life. Most patients have recurrent infections; bone marrow examination shows a myeloid maturation arrest. Rare patients may exhibit additional features such as seizures, learning difficulties, or cataracts, which are more commonly observed in patients with MGCA7 (616271). However, patients with SCN9 do not have 3-methylglutaconic aciduria, and most have normal neurologic function (Warren et al., 2022). For a discussion of genetic heterogeneity of severe congenital neutropenia, see SCN1 (202700).