Arthritis and arthralgia may be present in 4%-23% of patients with primary biliary cirrhosis. One report indicates that many more have radiologic abnormalities of erosive arthritis but have no symptoms. About 50% of patients with hemochromatosis and about 25% of patients with chronic active hepatitis develop arthritis or arthralgias; up to 40% of patients with hepatitis virus hepatitis have arthralgia (usually not true arthritis); and arthritis may occasionally be found in patients with viral infections of various etiology (e.g., rubella). Patients with cancer may develop joint symptoms due to direct extension from or a reaction to a nearby primary site or from joint area metastasis. Joint metastasis usually involves one of the knees and is most often due to carcinoma of the lung or breast. Metastasis to the hand is most often due to lung carcinoma. Childhood acute leukemia rather frequently appears to produce joint pain for a variety of reasons. Neoplasia have been associated with gout, vasculitis, and occasionally, syndromes resembling some of the collagen diseases. Occasionally, there may be arthritic symptoms without neoplastic joint involvement. Sarcoidosis may occasionally produce arthritis.