Novel ARPC1B mutation identified in a patient with recurrent eosinophilia

Immunodeficiency disorders linked to cytoskeleton defects are rare and complex, often presenting with diverse clinical features. This case report highlights a patient with recurrent eosinophilia and a novel homozygous ARPC1B mutation, expanding our understanding of genetic factors in immune-related conditions.

A 2-month-old female patient was admitted with recurrent fever and eosinophilia. She had a history of hospitalization for fever, bloody diarrhea, and vomiting. Physical examination revealed Simian creases, blue sclerae, anteverted ears, a high palate, and a depressed nasal bridge. Laboratory tests showed elevated eosinophils, lymphocytes, and immunoglobulins, along with thrombocytopenia. Imaging revealed focal low-density areas in the lungs and erythematous lesions on the cheeks.

Genetic analysis through whole-exome sequencing identified a novel homozygous variant in the ARPC1B gene (c.1081-5T>G) and compound heterozygous variants in the CFTR gene. The ARPC1B variant, located in a highly conserved region, was predicted to affect splicing. Immunofluorescent staining confirmed the absence of ARPC1B expression in the patient's cells.

The patient's clinical presentation, including recurrent infections, eosinophilia, and immunodeficiency, aligns with known ARPC1B-related disorders. However, this case uniquely presents without thrombocytopenia or high IgE levels, suggesting variability in clinical manifestations based on specific mutations. The concomitant CFTR variants may contribute to the patient's symptoms, though their exact impact remains unclear.

This case underscores the importance of considering genetic factors in patients with recurrent infections and eosinophilia. The identification of a novel ARPC1B mutation highlights the need for further research into the genotype-phenotype correlations and potential targeted therapies for these rare disorders.