ARPC1B is a key factor for ARP2/3 complex that is involved in actin branching from an existing filament. Bi-allelic mutations in the ARPC1B gene cause ARPC1B deficiency characterized by combined immunodeficiency (CID). ARPC1B deficiency is characterized by recurrent invasive infections, eczema, skin vasculitis, colitis, bleeding tendency, leukocytosis, T cell lymphopenia, eosinophilia, thrombocytopenia and hyper-IgE. Here we report a case of ARPC1B deficiency.
We used flow cytometry to characterize defects in T cells. Genetic analysis was performed by next-generation sequencing and Sanger sequencing.
A two-month-old boy was referred to our hospital with persistent oral moniliasis, pneumonia, cleft palate and congenital heart defects. His parents are non-consanguineous. The patient had a sister with cleft palate who died from sepsis. Laboratory evaluation showed anemia, marked leukocytosis, eosinophilia and normal platelet count. IgG, IgA, IgM and IgE levels were high. Direct-Coombs were positive. Percentages of CD3+, CD4+, CD4+CD45RA+ and CD4+CD45+CD31+T cells were low. T cell activation with PHA was inadequate. Echocardiography showed PFO and pulmonary stenosis. The patient was diagnosed with CID and autoimmune hemolytic anemia. IVIG and antimicrobial prophylaxis were initiated. HSCT could not be performed, because he did not have matched family donor. The patient died due to sepsis. Genetic analysis revealed a homozygous frameshift mutation in ARPC1B gene (p.H206YfsTer222), which was confirmed by Sanger sequencing. Both parents were heterozygous for the variant.
Unlike other patients, our patient had cleft palate and cardiac anomalies, and no thrombocytopenia. Early diagnosis and HSCT is crucial for survival of these patients.