Differential diagnosis of arthritic symptoms in a patient with cancer:
(1) pre-existing arthritis
(1a) degenerative osteoarthritis (many patients with cancer are older)
(1b) rheumatic disease (some patients with autoimmune disease are at risk for malignant lymphoma or other malignancies)
(2) metastasis to the joint or periarticular bone
(2a) symptoms directly related to effects of tumor in the bone adjacent to a joint (without direct joint involvement or reaction)
(2b) collapse of the articular surface secondary to loss of structural support
(2c) secondary reaction in the synovium to tumor in adjacent bone (uncommon)
(2d) metastatic implants to the synovium (rare)
(3) secondary gout following chemotherapy
(4) pyogenic arthritis
(4a) Streptococcus bovis or Clostridium species in bowel cancer
(5) radiation injury
(5a) osteonecrosis
(5b) fracture
(6) hypertrophic osteoarthropathy (clubbing), typically associated with lung cancer
(7) paraneoplastic effect or malignancy-related rheumatic disease
(7a) Sjogren's syndrome
(7b) dermatomyositis
(7c) lupus erythematosus
(7d) carcinoma polyarthritis (with asymmetric involvement)
