Nationwide Laboratory Surveillance of Progressive Multifocal Leukoencephalopathy in Japan: Fiscal Years 2011-2020

Area of Science:

• Neurology
• Virology
• Infectious Diseases

Background:

• Progressive multifocal leukoencephalopathy (PML) is a severe demyelinating disease attributed to JC virus (JCV) infection.
• PML primarily impacts individuals with compromised cellular immunity, and its non-reportable status complicates national surveillance efforts.
• JC virus (JCV) testing in cerebrospinal fluid (CSF) via polymerase chain reaction (PCR) is crucial for PML diagnosis in Japan.

Purpose of the Study:

• To elucidate the epidemiological profile of PML cases in Japan over a decade (FY2011-2020).
• To analyze clinical characteristics, geographic distribution, and demographic patterns of PML patients.
• To assess the impact of enhanced surveillance and ultrasensitive PCR on early PML detection.

Main Methods:

• Analysis of patient data from 1537 suspected PML cases undergoing CSF-JCV PCR testing between FY2011 and FY2020.
• Evaluation of clinical information, including underlying conditions, age, sex, and geographic data.
• Comparison of detection rates and disease stages over the study period, particularly noting advancements in the latter five years.

Main Results:

• Out of 1537 suspected PML cases, 288 (18.7%) tested positive for CSF-JCV.
• Detailed analysis revealed distinct patterns in geographic distribution, age, and sex among PML patients.
• The implementation of ultrasensitive PCR and increased clinical awareness facilitated earlier detection of JCV in CSF during the latter half of the study.

Conclusions:

• This study provides a comprehensive overview of PML epidemiology in Japan based on a decade of diagnostic testing.
• Findings highlight the utility of PCR-based JCV detection in CSF for PML diagnosis and surveillance.
• Improved diagnostic sensitivity and clinical vigilance contribute to earlier identification of PML, aiding timely management of both PML and its predisposing conditions.