Giant cell arteritis and polymyalgia rheumatica: role of viral infections.

We performed a multicenter case-control study on incident cases of giant cell arteritis and polymyalgia, and tested for viruses known to induce multinucleated giant cells in human pathology. IgM directed against Human parainfluenza type 1 virus were shown to be significantly associated with the onset of the disease in 40% of the cases, versus 20% of the controls.