Mumps is a childhood disease with declining incidence in the western world and arthritis is a rare complication associated to the disease. Various presentations exist making diagnosis even more challenging. The mechanisms responsible for the joint involvement remain largely unknown but the timing of onset of the symptoms usually coincide with the rise in antibody titers arguing for an immunologic mediated response. We hereby report a rare case of polyarthritis in the onset of epididymoorchitis due to mumps infection in a HIV infected male patient. Elevated IL-6 serum level in our patient suggests that this cytokine may be an interesting biomarker for the diagnosis of mumps related arthritis.