Adverse effects of TNF-alpha inhibition include leukopenia, elevated liver enzymes, infusion-related reactions, infections (including reactivation of herpes zoster and latent tuberculosis and new infections with fungi such as histoplasmosis), hypersensitivity reactions, malignancy, inflammatory demyelination of the CNS and rarely progressive multifocal leukoencephalopathy [31,32]. This evidence concerns the gene TNF and progressive multifocal leukoencephalopathy.