1. PML appearance in natalizumab cases may include enhanced lesions and even ring enhancing lesions unlike HIV associated PML
2. JC virus must be ordered as ultrasensitive assay as routine assay limit of sensitivity is around the fifty percentile of the (low) number of copies seen in some cases of Tysabri associated PML
3. PML presentation can be any type of new neuro abnormality including aphasia, heimparesis, hemisensory loss and others.
4. PML cases increase with Tysabri exposure up to two years but is not clear about more than two years. Prior immunosuppressive therapy increases the risk of PML
5. IRIS occurs after removal of natalizumab with sometimes precipitous decline in patient's status and even death.MRI usually shows GD+ enhancement, within 1-6 weeks after removing natalizumab.
6. IRIS prevention is reason for using Solumedrol one gram iv per day for five days followed by long taper
