Sarcoidosis presenting as progressive multifocal leukoencephalopathy in an apparently immunocompetent adult

Neurological involvement in sarcoidosis is termed as neurosarcoidosis. It usually leads to cranial neuropathies, although it can involve any part of the neuroaxis. Although sarcoidosis is a proinflammatory state, there is an associated anergic state demonstrable by a feeble tuberculin response. Lymphocytic sequestration in granulomas can be associated with peripheral CD4 lymphocytopenia (40% of patients with sarcoidosis) predisposing to opportunistic infections. Here we have described a young, otherwise immunocompetent male presenting with subacute onset right hemiparesis with motor aphasia, who was diagnosed to have progressive multifocal leukoencephalopathy (PML) secondary to pulmonary sarcoidosis. We want to emphasize that PML should be considered as a differential in all cases of secondary demyelination (even apparently immunocompetent individuals) as early diagnosis and treatment of the underlying cause is likely to yield better outcomes.