Retroviral expression in a patient who has paraarticular ossification

Reverse transcriptase activity is reported in the mononuclear blood cells isolated from a patient in whom paraarticular ossification developed after surgery for an aneurysmal bone cyst. The enzyme was purified to apparent homogeneity by chromatography before being characterized biochemically for its template specificity and ionic requirement. The enzyme was able to transcribe poly(rA).(dT)12-18 very efficiently in the presence of Mn++ ions. Viral particles were observed in the HuT-78 cell line, cocultured with the mononuclear cells of the patient. No viral particles were observed in HuT-78 cells before the coculture. The patient was found seronegative for HIV-1, HIV-2, and HTLV-1. These results suggest that a new retrovirus infecting mononuclear blood cells may be involved in the development of ectopic ossification. This hypothesis is strengthened by the previous finding of a retrovirus in the mononuclear blood cells of a patient with benign osteopetrosis, and by the fact that HTLV-1 infected T-lymphocytes acquire the ability to secrete factors responsible for the lytic bone lesions observed in the patients. A family of human bone diseases that reflect T-cell dysfunction(s) and are caused by lymphotropic viruses may exist.