Severe congenital neutropenia (SCN) is a rare hematopoietic disorder, with estimated incidence of 1 in 200,000 individuals of European descent, many cases of which are inherited in an autosomal dominant pattern. Despite the fact that several causal genes have been identified, the genetic basis for >30% of cases remains unknown. We report a five-generation family segregating a novel single nucleotide variant (SNV) in TCIRG1. There is perfect cosegregation of the SNV with congenital neutropenia in this family; all 11 affected, but none of the unaffected, individuals carry this novel SNV. Western blot analysis show reduced levels of TCIRG1 protein in affected individuals, compared to healthy controls. Two unrelated patients with SCN, identified by independent investigators, are heterozygous for different, rare, highly conserved, coding variants in TCIRG1. : Model of VATPase showing that TClRGl protein is itʼs largest component. Homozygous mutations of TClRGl are a known cause of osteopetrosis. Heterozygous mutation of p.Arg736Ser in TClRGl is now associated with congenital neutropenia, presumable by impairing the differentiation or maturation or myeloid cells in the bone marrow.(Figure is included in full-text article.)