We describe here a novel c.137 + 5G > A intronic mutation in the SH2D1A gene of the signaling lymphocyte activation molecule (SLAM)-associated protein (SAP) in association with Epstein-Barr virus (EBV)-induced fatal infectious mononucleosis (FIM) in an 8-year-old male patient and his 3-year-old step brother.
Prior to EBV infection, most boys with the defective XLP gene appear to be clinically healthy EBV infection in males with the defective XLP gene leads to three main phenotypes: severe and mostly fatal infectious mononucleosis (58%), lymphoproliferative disorders mostly of B-cell origin (30%) and/or dysgammaglobulinemia (31%).
X-linked lymphoproliferative syndrome (XLP or Duncan disease) is characterized by extreme sensitivity to Epstein-Barr virus (EBV), resulting in a complex phenotype manifested by severe or fatal infectious mononucleosis, acquired hypogammaglobulinemia and malignant lymphoma.