Progressive multifocal leukoencephalopathy in a patient with occult hypogammaglobulinemia experiencing bilateral visual impairment

To our knowledge this case is one of only a handful worldwide to describe PML developing in a patient with presumed immunocompetence at presentation - there was no previous history of recurrent, chronic, or atypical infections. There has only been one other report of visual symptoms presenting as the primary complaint. The case illustrates the importance of ruling out organic, central nervous system pathology in patients presenting with visual loss and normal <i>objective</i> visual function tests such as slit lamp examination and OCT.