[BK and JC viruses--2 polyomaviruses causing disease in immunosuppressed patients].
BK and JC viruses are two polyoma viruses designated by the initials of the patients from whom they were first isolated. After the primary infection, usually occurring in childhood or early school age, the viruses become latent. Reactivation occurs during immunosuppression, and the BK virus has been shown to be the main cause of viral hemorrhagic cystitis in bone marrow transplanted patients, while the JC virus has been found to cause progressive multifocal leukoencephalopathy, PML. The paper consists in a report of results obtained with an established method for the amplification of BK and JC virus DNA. Of 20 urine specimens from patients with hemorrhagic cystitis, 13 were found to be BK virus-positive. Post-transplantation follow-up shows that the virus continues to remain detectable for long periods. JC virus positivity was found in central nervous system material (a cerebrospinal spinal fluid specimen in one case) from two PML patients.