Progressive multifocal leukoencephalopathy associated with immune dysregulation.

Area of Science:

• Neuroimmunology
• Viral Neurology

Background:

• Progressive multifocal leukoencephalopathy (PML) is a rare, opportunistic demyelinating disease of the central nervous system.
• PML is caused by the John Cunningham (JC) virus, typically in severely immunocompromised individuals.
• Subtle immune dysregulation can also predispose individuals to PML.

Purpose of the Study:

• To report a case of PML in a patient with autoimmune hepatitis-primary biliary cholangitis overlap syndrome on low-dose corticosteroids.
• To highlight diagnostic challenges and the utility of extended immune profiling in atypical PML presentations.

Main Methods:

• Case report of a woman in her 40s with autoimmune hepatitis-primary biliary cholangitis.
• Clinical assessment, MRI, cerebrospinal fluid (CSF) analysis for JC viral DNA, and comprehensive immunophenotyping.
• Analysis included CD4+, CD8+, CD19+ T-cell and B-cell counts, and immunoglobulin levels.

Main Results:

• The patient presented with cerebellar symptoms and MRI findings consistent with PML.
• JC viral DNA was detected in CSF.
• Despite normal T-cell counts, immunophenotyping revealed significant B-cell lymphopenia, polyclonal hypergammaglobulinaemia, and elevated free light chains, indicating functional immunodeficiency.

Conclusions:

• PML diagnosis can be challenging in patients with seemingly preserved T-cell immunity.
• Extended immune profiling, including B-cell enumeration and immunoglobulin analysis, is valuable for atypical PML cases.
• Therapeutic decisions require balancing immune reconstitution with autoimmune disease management.