JC virus granule cell neuronopathy in the setting of chronic lymphopenia treated with recombinant interleukin-7.

JC virus (JCV) is a human polyomavirus that infects the central nervous system (CNS) of immunocompromised patients. JCV granule cell neuronopathy (JCV-GCN) is caused by infection of cerebellar granule cells, causing ataxia. A 77-year-old man with iatrogenic lymphopenia presented with severe ataxia and was diagnosed with JCV-GCN. His ataxia and cerebrospinal fluid (CSF) improved with intravenous immunoglobulin, high-dose intravenous methylprednisolone, mirtazapine, and mefloquine. Interleukin-7 (IL-7) therapy reconstituted his lymphocytes and reduced his CSF JCV load. One month after IL-7 therapy, he developed worsening ataxia and CSF inflammation, which raised suspicion for immune reconstitution inflammatory syndrome. Steroids were restarted and his ataxia stabilized.

Somatic mutations rather than viral infection classify focal cortical dysplasia type II as mTORopathy.

PURPOSE OF REVIEW: Genetic studies in focal cortical dysplasia type II (FCD II) provided ample evidence for somatic mutations in genes associated with the mammalian target of rapamycin (mTOR) pathway. Interestingly, the mTOR pathway can also be activated by the E6 oncogene of human papilloma viruses, and available data in FCD II remain controversial. We review and discuss the contradicting etiologies. RECENT FINDINGS: The neuroembryologic basis of cortical development and timing of a somatic mutation occurring in proliferating neuroblasts can mechanistically link mTORopathies. When a somatic mutation occurs in proliferating neuroblasts at an early stage of their anticipated total number of 33 mitotic cell cycles, large hemispheric lesions will develop from their affected progeny. Somatic mutations occurring at later periods of neuroblast expansion will result in circumscribed and small FCD II. Recently published data did not support evidence for viral infection in FCD II. SUMMARY: Genetic and histopathological data rather than viral infection classify FCD II into the spectrum of mTORopathies. Size and extent of the resulting cerebral lesion can be well explained by timing of somatic mutations during cortical development.

Failure to detect human papillomavirus in focal cortical dysplasia type IIb.

OBJECTIVE: Recent studies have reported evidence of human papillomavirus 16 (HPV-16) in a very high proportion of pathological specimens of focal cortical dysplasia type IIb, but not in control specimens, motivating the proposal that viral infection during fetal development may play a causal role in the pathogenesis of focal cortical dysplasias. However, the significance of the association between HPV infection and focal cortical dysplasia type IIb, and its reproducibility across surgical centers, remain unclear. Here we sought evidence for HPV-16 in an independent cohort of surgical specimens. METHODS: We identified 14 specimens of focal cortical dysplasia type IIb from a single surgical center between 1995 and 2013. Multiple methods were used to establish presence or absence of HPV, including DNA polymerase chain reaction, conventional in situ hybridization, chromogenic in situ hybridization, and immunohistochemistry for p16. RESULTS: We found no conclusive evidence of HPV in any of the specimens. All but 1 of the cases were negative by >1 method. INTERPRETATION: These results raise questions about the prevalence of HPV infection in focal cortical dysplasias and about its potential importance as a causative agent.