Mutations of the X-linked lymphoproliferative disease gene SH2D1A mimicking common variable immunodeficiency

Common variable immunodeficiency (CVID) and X-linked lymphoproliferative (XLP) disease are two immunodeficiencies that may share a similar immunological phenotype making differential diagnosis difficult. We report two patients initially diagnosed as affected with CVID who, using molecular analysis, have been subsequently found to be affected with XLP disease. Distinguishing between these two diseases is essential since they have different prognosis, treatment and genetic counselling. Conclusion: current techniques, such as genetic analysis of the SH2D1A gene and expression of signalling lymphocyte activation molecule-associated protein, allow a definite diagnosis of X-linked lymphoproliferative disease.