It is inflammation of the testis caused by autoimmune disease after viral infections like mumps. It can manifest as enlargement of the testis. It is most common in boys past puberty and rare before the age of 10.
Approximately 30% of patients who have mumps develop orchitis during the course of the illness. Lymphocytic infiltration in to testis and circulating antibodies to the sperms and the germinal cells leads to this disease. It usually develops 4 to 6 days after the attack.
In one-third of orchitis cases it is induced by mumps. It leads to testicular atrophy (shrinking of the testicles). Chronic orchitis may cause mild testicular pain or swelling and may look like a tumor.
Hence distinguishing autoimmune orchitis from a tumor is the main challenge. This is determined by biopsy and deoxyspergualin (an immunosuppressant) might be useful in prevention or treatment of human immuno inflammatory orchitis.