Severe congenital neutropenia in two siblings related to HAX1 mutation without neurodevelopmental disorders

Severe congenital neutropenia (SCN) is a rare primary myelopoiesis disorder, characterized by reduced absolute neutrophil counts from birth, increased susceptibility to recurrent and life-threatening infections, and a preleukemic predisposition. Herein, we describe two siblings with SCN born from consanguineous parents who were referred for complaints of recurrent cutaneous infections, gingivitis, purulent otitis media, and both lower and upper respiratory tract infections. Bone marrow aspiration of one patient demonstrated a maturation arrest in the myeloid lineage at the promyelocyte-myelocyte stages. Genetic analysis revealed a homozygous mutation in exon 2 c.130-131insA; p.W44X in the HAX1 gene. Although identical mutations were detected in both siblings, there was a clear discrepancy between the clinical course of the brother, who eventually required granulocyte colony stimulating factor (G-CSF) therapy, and the sister, who did not. Although SCN is a rare disorder, the early onset of recurrent infections and severe neutropenia, especially in children born from consanguineous parents, should always raise suspicion and warrant further evaluation.