Progressive multifocal leukoencephalopathy in a patient with occult hypogammaglobulinemia experiencing bilateral...

Progressive multifocal leukoencephalopathy (PML) is a rare, lethal, demyelinating disease classically seen in profoundly immunosuppressed individuals. It is caused by intracerebral infection by John Cunningham polyomavirus (JCV). We report a rare case of PML in a man with presumed immunocompetence at presentation experiencing bilateral painless visual impairment.

A 60-year-old man with a 3-week history of bilateral painless visual impairment attended our ophthalmology department. Unusually, he navigated around the room well and was able to read 4 of 13 Ishihara test plates in spite of a best-corrected visual acuity of counting fingers at 1 m bilaterally. Slit lamp examination, routine blood tests and optical coherence tomography (OCT) of the maculae and discs were unremarkable. Diffuse hyperintense white matter lesions on T2-weighted magnetic resonance imaging of the brain and detection of JCV within the parietal lobe tissue obtained by biopsy confirmed PML. Additional investigations identified an underlying hypogammaglobulinaemia, which may have initiated PML. He received intravenous immunoglobulin but passed away 2 months after diagnosis.

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 objective visual function tests such as slit lamp examination and OCT.