A concise review of pulmonary sarcoidosis

Abstract

This is an update on sarcoidosis, focusing on etiology, diagnosis, and treatment. In the area of etiopathogenesis, we now have a better understanding of the immune response that leads to the disease as well as genetic factors that modify both the risk for the disease and its clinical outcome. Several groups have also identified possible agents as a cause for sarcoidosis. Although none of these potential causes has been definitely confirmed, there is increasing evidence to support that one or more infectious agents may cause sarcoidosis, although this organism may no longer be viable in the patient. The diagnosis of sarcoidosis has been significantly aided by new technology. This includes the endobronchial ultrasound, which has been shown to increase the yield of needle aspiration of mediastinal and hilar lymph nodes. The positive emission tomography scan has proven useful for selecting possible biopsy sites by identifying organ involvement not appreciated by routine methodology. It has also helped in assessing cardiac involvement. The biologic agents, such as the anti-tumor necrosis factor antibodies, have changed the approach to refractory sarcoidosis. There is increasing evidence that the clinician can identify which patient is most likely to benefit from such therapy. As new and more potent antiinflammatory agents have been developed, it is clear that there are other factors that burden the patient with sarcoidosis, including fatigue and sarcoidosis-associated pulmonary hypertension. There have been several recent studies demonstrating treatment options for these problems.

Figure 1.

Inflammatory response of sarcoidosis with formation of granuloma and subsequent resolution or persistence of disease. HLA = human leukocyte antigen; IFN = interferon; TCR = T cell receptor; TNF = tumor necrosis factor.

Figure 2.

An approach to diagnosis of pulmonary sarcoidosis.

Figure 3.

Rate of pulmonary hypertension in patients with sarcoidosis in various series across the world. The studies from Kyoto (114) and Detroit (115) examined a cohort of all patients with sarcoidosis. The studies from Milan (116), New York (53), and Cincinnati (54) were of patients with pulmonary symptoms referred for evaluation for pulmonary hypertension. Patients referred for lung transplant had the highest rate of pulmonary hypertension (117). The studies marked by open bars used echocardiography to determine pulmonary hypertension. The solid bar indicates those studies that used right-sided heart catheterization to determine pulmonary hypertension.