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General Information about Sarcoidosis

Sarcoidosis Week

Almost 140 years after the first known recorded description of sarcoidosis by Dr. Johnathon Hutchinson, this disease remains enigmatic. Sarcoidosis is a granulomatous disease with a female and young adult predominance that affects children and adults of all racial and ethnic groups.  In the US, the prevalence is highest in African Americans, with the peak incidence during the 4th decade of life. The diagnosis of sarcoidosis is established using clinical and radiologic findings alongside histologic evidence of noncaseating epithelioid-cell granulomas in the absence of organisms or particles. Although the etiologic agent remains unclear, there are reports of various environmental causes in a genetically susceptible host.

More than 90% of patients with sarcoidosis have skin, eye and lung involvement; thus, the environment, in part, likely plays a role in the development of the disease. Sarcoidosis is also associated with gene products, thus interactions between sarcoidosis susceptibility loci and the environment also likely exists. Do granulomas form to confine antigens, restrict inflammation, and protect tissue? Is granuloma formation independent of a particular antigen or is it, instead, the result of a traumatic insult? A cardinal feature of sarcoidosis is the presence of CD4+ T cells that interact with antigen-presenting cells to initiate the formation and maintenance of granulomas. Löfgren's syndrome, an acute presentation consisting of arthritis, erythema nodosum, and bilateral hilar adenopathy can also be observed. Interestingly, two thirds of patients with sarcoidosis generally have a remission within a decade of diagnosis.

Although these granulomas largely resolve in most patients, 25% will go on to develop pulmonary fibrosis with respiratory symptoms including cough, wheezing, dyspnea, and chest discomfort. Chest radiographs are used to classify sarcoidosis into four Scadding stages -based on radiographic patterns, not disease chronicity or pulmonary function. Most patients have airflow limitation and restrictive physiology, with reduced forced vital capacity and forced expiratory volume in one second. Patients can also have concurrent obstructive physiology and airway hyperreactivity that is poorly responsive to bronchodilator therapy.  Pulmonary arterial pressure elevations at rest and with exertion from fibrosis or granulomatous infiltration of the pulmonary arterioles can also be seen in patients with sarcoidosis.

There is no definitive diagnostic study, therefore, sarcoidosis remains a diagnosis of exclusion. The initial patient assessment should be comprehensive and include a multi-organ clinical evaluation with imaging studies, cardiac studies, and lab work. Subsequent assessments can occur every 3 months depending on disease severity. Systemic symptoms such as fatigue, night sweats, and weight loss are common. When organ function is threatened, the decision to treat should be made with either steroid or steroid-sparing agents. Transplantation should also be considered and offered early on in the disease course, if appropriate, since the 1 and 5-year graft survival rates for lung and liver transplants in patients with sarcoidosis are similar to those for lung and liver transplants from other diseases.

Although in recent years sarcoidosis researchers have made significant progress in understanding the immunology and genetics of the disease, we still have much to discover.  The ATS and the Foundation for Sarcoidosis Research support investigation to improve our understanding of the pathophysiology, management and treatment of sarcoidosis. In addition, the National Institutes of Health recently funded a study to analyze all of the genes expressed in the blood and lung fluid, and all of the microbes in the lungs in a large cohort of patients with sarcoidosis. The results of this study are currently being analyzed, and more funded research is needed to ensure that significant progress is made in understanding sarcoidosis. Sarcoidosis Week provides an opportunity for the ATS and the Foundation for Sarcoidosis Research to increase the knowledge and awareness of this enigmatic disease.

Quick Facts About Sarcoidosis

  1. While roughly 50% of people with sarcoidosis will go into remission within a year of displaying symptoms, an estimated 10-15% of cases become advanced with severe life-altering effects.
    Source: https://www.stopsarcoidosis.org/what-is-sarcoidosis/

  2. While sarcoidosis can affect people of all races and ethnicities, it disproportionately affects people of African American and Scandinavian descent in both prevalence and severity.
    Source: https://www.stopsarcoidosis.org/what-is-sarcoidosis/causes-risk-factors/

  3. The average age of diagnosis in the US is 55, though people of all ages can be affected and are often diagnosed anywhere between ages 20 and 70.
    Source: https://www.stopsarcoidosis.org/what-is-sarcoidosis/diagnosis/

  4. The prevalence of sarcoidosis worldwide is estimated at 1,238,000 people, affecting an estimated 200,000 Americans.
    Source: https://www.stopsarcoidosis.org/what-is-sarcoidosis/