A Boy with X-Linked Inhibitor of Apoptosis Protein (XIAP) Deficiency as the Initial Presentation of Pure Red Cell Aplasia / 임상소아혈액종양

ABSTRACT

X-linked inhibitor of apoptosis protein (XIAP) deficiency is a rare immunodeficiency disorder. A 13-month-old boy was diagnosed with pure red cell aplasia (PRCA) and treated with steroid and cyclosporine. Bone marrow showed diminished erythroid precursors, and positive results for Parvovirus B19 and Cytomegalovirus (CMV) infection. A genetic study of Diamond-Blackfan anemia was negative. Five months later, he was admitted due to fever and lymphadenopathy. PCR showed still positive for the Parvovirus, CMV, and Epstein-Barr virus (EBV). He was diagnosed with diffuse large B-cell lymphoma that was positive for EBV. The patient received chemotherapy with R-CHOP, and achieved complete remission. Immunoglobulin (Ig) levels were within an age-matched normal range until the completion of chemotherapy. Subsequently, he was admitted nine times due to recurrent pneumonia and acute otitis media between two and eight years old. We reanalyzed the Ig levels and lymphocyte subsets: IgG, IgA, and IgM were 30 mg/dL, below 1.0 mg/dL, and 36 mg/dL, respectively. Lymphocyte subsets showed nearly absent CD19 (+) cells, but T- and NK cell counts were within normal ranges. A genetic study showed a hemizygous inframe deletion mutation in exon 4 of the IAP gene without the SH2D1A mutation, consistent with a XIAP deficiency. Therefore, he was diagnosed with XIAP deficiency. Genetic analysis of his mother, aunt and elder sister showed that they were carriers of the same gene mutation. He receives intravenous Ig regularly with follow-up, and still requires a low dose steroid to maintain hemoglobin level. We report XIAP deficiency as initial presentation of PRCA.