The polyomavirus JC (JCV) is the causative agent of progressive multifocal leukoencephalopathy (PML) in immunosuppressed patients. JCV is a neurotropic virus that causes productive infection of oligodendrocytes and restrictive infection of astrocytes. The concept of narrow host cell selection of JCV has been challenged by recent case studies. It was reported that JCV can also cause productive infection of cerebellar granular neurons (CGN) independently of PML infection in the cerebral hemisphere. This novel syndrome was called JCV granule cell neuronopathy (JCV-GCN).1,2 Isolated cerebellar degeneration due to JCV infection restricted to the cerebellum in the absence of typical features of PML in HIV disease was only reported in one case.1 Hyperimmunoglobulinemia E (hyper-IgE) and eosinophilia have been described in some HIV-infected patients.3 The immunoglobulin E (IgE) level was correlated with immune status. Very high IgE level (20- to 100-fold above normal) usually occurred with significant decrease in CD4 cells. These patients usually presented with atopic dermatitis …