Purpose of review The availability of a growing number of immunomodulatory medications over the past few years has been associated with various JC Virus (JCV) associated brain syndromes in patients with autoimmune diseases, including multiple sclerosis, Crohn’s disease and psoriasis which had not been previously recognized as predisposing factors for progressive multifocal leukoencephalopathy (PML). This review covers the three novel syndromes discovered in the last decade which are caused by JCV infection of neurons and meningeal cells. Recent findings For more than 30 years, JCV was thought to exclusively infect oligodendrocytes and astrocytes in the white matter of the brain of immunosuppressed individuals. We now recognize that JCV-infected glial cells are frequently located at the gray-white matter junction or exclusively within the gray matter causing demyelination in the cortex. Mutations in JCV can trigger a change in tropism leading to involvement of other cell types, such as neurons and meningeal cells, causing clinically distinct entities. These new features of JCV infection provide challenges for clinicians taking care of affected patients and investigators studying the biology of this polyomavirus, its pathogenesis, and tropism. Summary We hope that increasing awareness of these syndromes will lead to early diagnosis, and pave the way for new avenues of research to better understand all aspects of JCV pathogenesis and develop efficient therapies for our patients. However, we need to remain vigilant and open to the possibility that additional JC variants or yet unknown polyomaviruses may be associated with neurological diseases as well.

Objective:To describe the compassionate use of interleukin-7 (IL-7) for treatment of progressive multifocal leukoencephalopathy (PML) in the setting of idiopathic CD8+ greater than CD4+ lymphocytopenia.Methods:A 66-year-old HIV-seronegative man presented with progressive language dysfunction. MRI showed hyperintense lesions in the left hemispheric white matter with mild contrast enhancement. A brain biopsy performed 4 months after symptom onset established the diagnosis of PML. The patient had profound lymphocytopenia with absolute lymphocyte count (ALC) at 168 cells/μL, 87 CD4+ T cells/μL, and 7 CD8+ T cells/μL. There was no evidence of hematologic malignancy or rheumatologic disease.Results:The patient received 3 intramuscular injections of IL-7 at a dose of 10 μg/kg per week with no adverse effects. ALC peaked at 595 cells/μL, CD4+ T cells at 301 cells/μL, and CD8+ T cells at 34 cells/μL 3 weeks after completion of treatment. His lesions on MRI stabilized and neurologic examination mildly improved. JCV-specific T-cell responses measured by intracellular cytokine staining were not altered after treatment with IL-7 but there was a marked increase in regulatory T cells.Conclusion:This case further supports the investigational use of IL-7 in patients who develop PML in the setting of ICL.Classification of evidence:This study provides Class IV evidence that for patients with ICL and PML, IL-7 improves PML-related-outcomes. The study is rated Class IV because it is a case report.

The presence of tumefactive brain lesions, nonspecific brain calcifications, liver disease, and retinal vasculopathy, coupled with suggestive family history, led to the RVCL diagnosis. This report contributes to the limited understanding of RVCL, which can cause brain lesions that mimic gliomas or tumefactive MS. Recognition of this entity may prevent unnecessary invasive procedures and inappropriate therapeutic interventions, and would allow for proper counseling of family members.