Sarcoidosis: immunology, rheumatic involvement, and therapeutics

Sarcoidosis is a systemic granulomatous disorder of unknown cause. It has p rotean manifestations and can affect any organ, including bones, joints, mu scles, and vessels, This article reviews the most recent information on the immunologic and inflammatory pathogenesis of sarcoidosis and its implicati ons for therapy. Sarcoidosis results from an overexuberant T cell-mediated immune response to the unknown antigen. This antigen presentation/T cell an tigen recognition event occurs in a microenvironment that is suffused in pr oinflammatory cytokines and growth factors that promote cell attraction, ad hesion, permeability changes, further cytokine production, and release. An amplified cellular immune response ensues, leading to granuloma formation a nd fibrosis. The article summarizes the new developments in the medical lit erature related to the rheumatologic manifestations and their detection and management in sarcoidosis patients. Osseous involvement in sarcoidosis is often underdiagnosed because it can be asymptomatic. New imaging techniques improve detection. Management of osteoporosis in sarcoidosis patients requ ires special attention because these patients often have an underlying diso rder in calcium metabolism that results in hypercalcuria and hypercalcemia. Joint manifestations, such as the classic Lofgren syndrome with accompanyi ng erythema nodosum, may be self-limited or may become chronic, presenting an ongoing therapeutic challenge. Sarcoidosis vasculitis can be devastating , affecting virtually any vessel in any organ and causing significant morbi dity, Muscle involvement, like the bony involvement, is underdiagnosed. Sym ptoms of muscle weakness, aches, tenderness, and fatigue should prompt cons ideration of occult sarcoid myositis, often with accompanying neurogenic at rophy. Sarcoidosis treatment usually starts with a period of observation be fore pharmacologic intervention. Corticosteroids remain the first-line ther apy. Alternatives to corticosteroids are often introduced either because of steroid intolerance or in an attempt to reduce steroid dose and side effec ts. The advantages and disadvantages of these second line therapies are rev iewed. Medical vigilance, with attention to new patient symptoms, is import ant in the management of sarcoidosis, because of the tendency of this disea se to present in so many and diverse patterns. Curr Opin Rheumatol 2001, 13 :84-91 (C) 2001 Lippincott Williams & Wilkins, Inc.