Mutations in Dedicator of cytokinesis 8 (DOCK8) are a rare cause of combined immunodeficiency associated with atopy, infectious susceptibility, and risk for malignancy. We describe a 22-year-old male with a diagnosis of B cell lymphoblastic leukemia followed by Epstein-Barr virus (EBV)-associated diffuse large B cell lymphoma (DLBCL) with compound heterozygous mutations in DOCK8 and normal intracellular DOCK8 protein expression. Here, B cell lymphoblastic leukemia followed by EBV-associated DLBCL led to the discovery of DOCK8 deficiency. For instances of high clinical suspicion despite normal DOCK8 protein expression, additional functional testing is critical to make a diagnosis. Understanding the spectrum of DOCK8 mutants and their phenotypes will improve our understanding of DOCK8 deficiency.
Keywords: B cell lymphoblastic leukemia; combined immunodeficiency; dedicator of cytokinesis 8; diffuse large B cell lymphoma.