Background: Progressive multifocal leukencephalopathy (PML) is a rare, sometimes fatal viral disease in patients with primary or secondary immunosuppression.
Case description: A 57-year-old immunocompetent female with intractable Holmes tremor and elongated unique brainstem lesion reported to our hospital. The cerebrospinal fluid (CSF) screening for John Cunningham virus was negative and the diagnosis was established by brain biopsy. The course was rapidly fatal.
Conclusion: This atypical presentation of PML in an immunocompetent patient illustrates that diagnosis can be missed without brain biopsy.
Keywords: Brainstem; Holmes tremor; JC virus; immunocompetence; progressive multifocal leukencephalopathy.