Sarcoidosis

Abstract

Sarcoidosis is a multisystemic disorder of unknown origin characterized by the accumulation of lymphocytes and mononuclear phagocytes that induce the formation of noncaseating epithelioid granulomas. Virtually any organ can be affected; however, granulomas most often appear in the lungs or the lymph nodes. Cutaneous disease occurs in up to 20 % of cases.

The cutaneous manifestations are variable; based on the histological findings, skin lesions of sarcoidosis have been classified as “specific” (when a typical granulomatous infiltrate is present in the sample tissue) and “nonspecific.” Specific lesions include lupus pernio, maculopapular eruptions, subcutaneous nodules, infiltrative scars, and plaques. Nonspecific manifestations, except for erythema nodosum, are uncommon, such as calcifications, erythema multiforme, prurigo, nail clubbing, and Sweet syndrome.

If the diagnosis of sarcoidosis is strongly suspected on clinical and pathological grounds, then further investigation should be tailored to identify systemic disease, in order chest X-ray, pulmonary function tests, electrocardiogram, full blood count, biochemistry, serum immunoglobulins, and a 24-h urinary calcium assay. Measurement of serum angiotensin-converting enzyme (ACE) may be helpful in monitoring disease activity.

Cutaneous sarcoidosis is known as the “great imitator” because of its widely variable morphologies; there is a large group of skin diseases that can enter the differential diagnosis with it, such as acne, rosacea, syphilis, polymorphous light eruption, lupus erythematosus, lichen planus, lupus vulgaris, necrobiosis lipoidica, morphea, leishmaniasis, nummular eczema, cutaneous T-cell lymphoma, B-cell lymphoma, Kaposi sarcoma, and others.