Late-Onset Combined Immunodeficiency presenting with Progressive Multifocal Leukoencephalopathy and associated Immune Reconstitution Inflammatory Syndrome

Progressive multifocal leukoencephalopathy (PML) can rarely occur in individuals with occult immuno-suppression. Here, we describe the case of an adult man who presented with PML, in whom CD4+ lymphocy-topenia and hypogammaglobulinemia were subse-quently identified, leading to a diagnosis of late-onset combined immunodeficiency. Intravenous immuno-globulin replacement therapy was initiated. His clinical course, though complicated by immune reconstitution inflammatory syndrome, was favorable.