Proportional to the growth rate of its clinical expression, the last decades have seen an increase on JC Virus diagnosis testing, and on therapeutic and symptoms management plans. Whether isolated or associated to retroviral therapy, the relationship of JC Virus to HIV allowed us to delve a little deeper into the knowledge of its behavior. Now as new immune-modulating and immune-suppressing therapies are developed, its clinical expression has become broader and more complexly, thereby our need is to develop more precise diagnosis and therapeutic plans.