X-LINKED INHIBITOR OF APOPTOSIS DEFICIENCY IN A PATIENT WITH ADULT-ONSET RECURRENT FEBRILE ILLNESSES

Abstract

<h3>Introduction</h3> X-linked inhibitor of apoptosis (XIAP) deficiency is a primary immunodeficiency caused by a mutation in the gene XIAP. It is commonly associated with hemophagocytic lymphohistiocytosis (HLH), recurrent splenomegaly, and inflammatory bowel disease (IBD), as well as hypogammaglobulinemia. We report a case of an adult with late diagnosis of XIAP deficiency in the setting of recurrent febrile illnesses. <h3>Case Description</h3> An 18-year-old Caucasian male presented with fever and generalized lymphadenopathy without other localizing symptoms, which was attributed to cytomegalovirus infection. He recovered without specific treatment, but throughout adulthood he had recurrent infections including pneumonia, appendicitis, cholecystitis, epididymitis, sinusitis, and aseptic meningitis. These infections were often associated with high fever, transaminase elevation, and inflammatory marker elevation. At age 41 he demonstrated persistent hypogammaglobulinemia (IgG 610-635, reference range 767-1590 mg/dl; IgM 28-33, reference range 37-286 mg/dl), elevated antinuclear antibodies, and poor Pneumovax response (adequate response to serotypes 9V, 2, 6B). He denied family history of similar issues. Common variable immunodeficiency (CVID) was considered, but subsequent genetic testing showed a pathologic variant in XIAP gene (c.712C>T/p.Arg238*), leading to a diagnosis of XIAP deficiency. The patient was started on IVIG and Anakinra with good response to treatment. <h3>Discussion</h3> This case highlights the importance of considering genetic testing even in adults with delayed onset of symptoms. The clinical phenotype and presentation of XIAP deficiency is variable and can often mimic more common diseases such as CVID. Even in patients without a history of IBD or HLH, genetic testing to detect XIAP deficiency should still be considered given its variable presentation.