It's unsettling that a person can have asymptomatic PML. This abstract describes such a case, in an MS patient taking Tysabri.
From PubMed, November 7, 2015:
J Clin Neurosci. 2015 Nov 2. pii: S0967-5868(15)00517-2.
Asymptomatic progressive multifocal leukoencephalopathy during natalizumab therapy with treatment
Fabis-Pedrini MJ1, Xu W2, Burton J1, Carroll WM1, Kermode AG3.
Author information
1Centre for Neuromuscular and Neurological Disorders, Western Australian Neuroscience Research Institute, The University of Western Australia, Sir Charles Gairdner Hospital, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, WA 6009, Australia.
2Centre for Neuromuscular and Neurological Disorders, Western Australian Neuroscience Research Institute, The University of Western Australia, Sir Charles Gairdner Hospital, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, WA 6009, Australia; Department of Neurology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
3Centre for Neuromuscular and Neurological Disorders, Western Australian Neuroscience Research Institute, The University of Western Australia, Sir Charles Gairdner Hospital, 4th Floor, A Block, QEII Medical Centre, Verdun Street, Nedlands, WA 6009, Australia; Institute of Immunology and Infectious Diseases, Murdoch University, Murdoch, WA 6150, Australia. Electronic address: kermode@me.com.
We report a case of asymptomatic progressive multifocal leukoencephalopathy (PML) detected on regular MRI screening in a 40-year-old patient with subsequent benign course with 12-months follow-up.
The patient had a history of aggressive inflammatory multiple sclerosis, prior mitoxantrone therapy, Stratify John Cunningham Virus test positivity (Quest Diagnostics, Madison, NJ, USA), and 5 years of natalizumab monotherapy. The initial MRI detection of PML was both atypical and subtle. Early diagnosis and intervention, and pre-emptive treatment for immune reconstitution inflammatory syndrome with high dose steroids, as well as empirical mirtazapine and mefloquine, were associated with a benign PML disease course and outcome.
The abstract can be seen
here.