A case of progressive multifocal leukoencephalopathy with hypogammaglobulinemia and a TCF3 mutation.

Progressive multifocal leukoencephalopathy (PML) is a rare and potentially fatal demyelinating disease of the central nervous system (CNS) caused by JC virus; it was previously seen predominantly in immunocompromised patients and those under intense immune suppression. Here, we report the case of a patient with PML with hypogammaglobulinemia and a heterozygous mutation in the TCF3 gene. As the TCF3 gene has been demonstrated to play an important role in the B cell differentiation process and the patient had no other medical history of the immune system, he was diagnosed with common variable immunodeficiency (CVID). To our knowledge, this is the first case of patient with a TCF3 gene deficiency and hypogammaglobulinemia who developed PML.