Cancer-associated neuromusculoskeletal syndromes. Recognizing the rheumatic-neoplastic connection.

Several cancer-associated neuromusculoskeletal syndromes initially described in isolated case reports were later defined more thoroughly in population-based and prospective studies. The pathophysiologic basis of various paraneoplastic neurologic degenerations also has been established by use of cellular and molecular methods. Tumors may release humoral factors that affect the function of distant tissues. Tumor antigens can be recognized by the immune system, leading to generation of antibodies or T cells that can target normal tissue. Such mechanisms have been described for tumor-associated myasthenia gravis and paraneoplastic cerebellar degeneration. Epidemiologic data support the association between rheumatic diseases (e.g., dermatomyositis, Sjögren's syndrome, systemic sclerosis, hypertrophic osteoarthropathy) and cancer. The pathogenesis of this association remains to be clarified.