The cause of sarcoidosis is unknown but several possibilities exist. The disease may result from a hypersensitivity response—possibly from T-cell imbalance—to such agents as atypical mycobacteria, fungi, and pine pollen. The incidence is slightly higher within families, suggesting a genetic predisposition. Chemicals may trigger the disease (zirconium or beryllium lead to illnesses that resemble sarcoidosis).

Although the exact mechanism of the disease is unknown, research suggests a T-cell problem and, more specifically, a lymphokine production problem. In other granulomatous diseases, such as tuberculosis, granuloma formation occurs from inadequate pathogen clearance by macrophages. These macrophages require the help of T cells that secrete lymphokines, which in turn activate less effective macrophages to become aggressive phagocytes. Lack of lymphokine secretion by T cells may help explain granuloma formation in sarcoidosis.

Sarcoidosis can eventually lead to pulmonary fibrosis, with resultant pulmonary hypertension and cor pulmonale.

The patient may report pain in the wrists, ankles, and elbows; general fatigue and a feeling of malaise; and unexplained weight loss. He may also complain of breathlessness and shortness of breath on exertion and have a nonproductive cough and substernal pain.

On inspection, you may observe erythema nodosum, subcutaneous skin nodules with maculopapular eruptions, and punched-out lesions on the fingers and toes. You may also note weakness and cranial or peripheral nerve palsies. When you inspect the nose, you may see extensive nasal mucosal lesions. Inspection of the eyes commonly reveals anterior uveitis.
Glaucoma and blindness occasionally occur in advanced disease.

You may be able to palpate bilateral hilar and right paratracheal lymphadenopathy and splenomegaly, and you may detect such arrhythmias as premature beats on auscultation.

A positive Kveim-Siltzbach skin test

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