CLPB deficiency-associated congenital neutropenia: A rare case report and literature review.

[RATIONALE] Congenital neutropenia (CN) encompasses a group of disorders characterized by impaired neutrophil differentiation, resulting in persistently low neutrophil counts in the peripheral blood. It presents with recurrent infections and an elevated risk of leukemia. Multiple genetic mutations have been implicated in the pathogenesis of neutropenia.

[PATIENT CONCERNS] This paper reports the case of a 3-year-2-month-old boy admitted with a 4-day history of cough and fever, accompanied by recurrent respiratory infections, neutropenia, and growth retardation. Whole-exome sequencing identified a mutation in the caseinolytic peptidase B homolog (CLPB) gene (NM_030813.6: c.1681C>T: p.R561W).

[DIAGNOSES] Although the initial genetic sequencing did not reveal mutations consistent with the clinical presentation, the child continued to experience recurrent infections. Upon reanalysis, a pathogenic CLPB-related mutation was detected, leading to the diagnosis of CN.

[INTERVENTIONS] During hospitalization, the patient received targeted antimicrobial therapy based on the identification of the pathogen. Following the confirmed diagnosis, he also received intermittent granulocyte colony-stimulating factor therapy.

[OUTCOMES] Administration of granulocyte colony-stimulating factor successfully maintained neutrophil counts above 0.5 × 109/L and significantly reduced the frequency of respiratory tract infections.

[LESSONS] CLPB deficiency should be considered in pediatric patients presenting with CN and concurrent neurological symptoms, as early recognition allows for the timely initiation of appropriate treatment strategies and contributes to improved clinical outcomes.