Severe congenital neutropenias (SCNs) are the rare heterogenous group of preleukemia bone marrow failure syndromes characterized by impaired differentiation of neutrophilic granulocytes and, as a result, severe chronic neutropenia. Patients with SCN are predisposed to recurrent, often life-threatening bacterial and/or fungal infections beginning in the first months of life. Molecular abnormalities in 10 genes have been identified that are responsible for SCNs. The pathophysiological mechanisms of SCNs are the subject of extensive investigation and are not fully known. The current review aims to summarize the studies exploring the biological role of SCN-associated genes and the effects of mutant genes in neutropenia pathogenesis. We mainly focus on the genetic mutations that lead to SCN1 to SCN9 and X-linked SCN (XSCN) to shed more light on the pathophysiology of these diseases.