X-linked lymphoproliferative disease (XLP), a genetic disorder characterized by immunodeficiency to Epstein-Barr virus (EBV) infection, has been linked to mutations in the SH2D1A gene. XLP patient displays EBV associated fulminant infectious mononucleosis or hemophagocytic lymphohistocytosis, hypogammaglobulinemia or malignant lymphoma. Here we report the clinical features, gene mutation and SAP expression on PBMCs of a Chinese patient with XLP and potential carriers.A 6 years old male patient and his maternal relatives were enrolled in this study. The patient was found to have with a renal Burkitt lymphoma on the right waist at 5 years of age by accident. His elder brother and a maternally related cousin both died of multiple systemic organ dysfunction syndrome (MODS) due to fulminant infectious mononucleosis (FIM) at the age of one year. The patient and his maternal relatives were subjected to detection of SAP expression on the PBMCs by flow cytometry and gene mutation analysis of SH2D1A by using PCR based on genomic DNA.The patient exhibited 536.9 copy/ml level of circulating EBV-DNA during remission. Sequence analysis showed that the patient harbored a nonsense mutation in exon 2 (C462T), resulting in a premature stop codon (Arg55X). His mother and some of the maternal relatives were proved to be carriers of this mutation. SAP expression from the patient was significantly reduced as compared to normal individual and the carriers.We identified a Chinese XLP case genetically. Assessment of SAP expression on PBMCs by flow cytometry seemed to be an effective rapid diagnostic method for this disease. Absence of EBV infection does not diminish the possibility of XLP.