Clinical phenotype and functional analysis of a rare XIAP/BIRC4 mutation

X-linked lymphoproliferative syndromes (XLP) are rare primary immunodeficiencies. Mutations within the XIAP/BIRC4 gene characterize XLP type 2 and cause XIAP deficiency. We present the case of a 5-year-old boy with a novel mutation of the XIAP/BIRC4 gene and describe the immunological phenotype for the first time. We characterized the distinct immunological phenotype and evaluated the family history accordingly.