Background: X-linked inhibitor of apoptosis (XIAP) deficiency is a rare inborn error of immunity which occurs secondary to mutations in the XIAP/BIRC4 gene. Disease onset usually manifests within the first few years of life, and is associated with a spectrum of clinical features, secondary to immune dysregulation. Males typically present with refractory chronic colitis, hemophagocytic lymphohistiocytosis, and severe and/or recurrent infections. Laboratory analysis may reveal hypogammaglobulinemia and cytopenias. At present, the only curative treatment is allogenic hematopoietic stem cell transplantation.
Case presentation: A 24-year-old gentleman, immigrant from the Democratic Republic of Congo, was referred to outpatient immunology for evaluation of an inborn error of immunity given a past medical history significant for refractory fistulizing Crohn's disease, arthritis, liver abscesses, prior disseminated tuberculosis, anemia, and recurrent infections. He had been asymptomatic throughout his childhood and adolescence, with no infections or symptoms of inflammatory disease until the age of 19, when he was diagnosed with Crohn's disease. He was soon after admitted to hospital and was diagnosed with hemophagocytic lymphohistiocytosis. Primary immunodeficiency gene panel testing revealed a nonsense variant XIAP c833C > G p.(Ser278*), which generates a premature stop codon at exon 2 (of total 7 exons). On flow cytometry analysis, XIAP protein expression was significantly reduced, confirming the diagnosis of XIAP deficiency.
Conclusion: This is one of the only documented reports of a patient with XIAP deficiency, presenting with symptom-onset in adulthood. This case highlights the need to maintain a high index of suspicion for XIAP deficiency in patients with the appropriate clinical presentation, despite advanced age of presentation.
Keywords: HLH; Inborn error of immunity; Stem cell transplant; XIAP.
© 2025. The Author(s).