De Novo Missense Variant c.170 C > A of ELANE in a Chinese Infant with Congenital Neutropenia: Case Report and Literature Review.

Congenital neutropenia (CN) is a rare hereditary blood disorder characterized by a significant reduction in neutrophils, making patients prone to recurrent and severe infections and even a risk of developing myelodysplastic syndrome or acute leukemia, often caused by the ELANE variants, and the complex relationship between ELANE variants and clinical phenotypes, as well as the natural course of the disease, remains unclear. We describe a case of CN in a Chinese infant caused by the De Novo missense variant c.170 C > A in the ELANE gene, presented with persistent neutropenia since the neonatal period, accompanied by recurrent infections. He did not receive G-CSF treatment due to the declination of his parents, but antibiotics were administered during infections or with high hsCRP levels. During the early neonatal stage, the patient consistently exhibited severe neutropenia (ANC < 0.5 × 10^9/L). Periodic fluctuations in neutrophil counts observed twice a week during particular months suggest a cyclical pattern. Until now, he still experiences varying degrees of neutropenia persistently, with ANC occasionally exceeding 1.0 × 10^9/L during infections. Multiple prediction scoring tools and models support the pathogenicity of this missense variant. This case highlights a rare pathogenic variant of ELANE, which, to our knowledge, is the first case of the variant c.170 C > A (p.Ala57Asp) of the intermediate phenotype of CN in mainland China and a rare variant globally, indicating phenotypic variability in ELANE-related neutropenia due to an Ala57 mutation. The clinical management of CN caused by ELANE variants poses a challenge for clinicians and deserves attention. Timely diagnosis, treatment, and extended follow-up are of paramount value.