<prompt> Answer this question truthfullyWhat are the conditions that can lead to the presentation of JC virus?  <response>: <reason> JC virus can present when the CD4 count is less than 200 or with immunosuppressants. The JC virus is a type of human polyomavirus that can cause a rare and often fatal brain disease called progressive multifocal leukoencephalopathy PML. PML typically occurs in people with weakened immune systems, such as those with HIVAIDS, cancer, or receiving immunosuppressive therapy. In people with HIVAIDS, PML is often a sign of advanced disease and occurs when the CD4 count drops below 200. The use of immunosuppressants, such as those used in organ transplantation, can also increase the risk of JC virus infection and PML. 