Sarcoidosis
Sarcoidosis is an inflammatory disease characterized by the formation of noncaseating granulomas in various organs, most commonly affecting the lungs, lymph nodes, skin, and eyes. The precise cause of sarcoidosis remains unknown, but it is believed to stem from an abnormal immune response to environmental triggers or infectious agents. Symptoms can include fatigue, cough, and skin lesions, and while some cases may resolve on their own, others may lead to chronic complications that cause organ damage. The incidence of sarcoidosis varies among ethnic groups, with higher rates observed in African Americans compared to Caucasians, and it typically presents in individuals aged 20 to 40. Diagnosis often involves ruling out other conditions through imaging technologies and biopsies, where granulomas are identified. For those with severe cases, corticosteroids are commonly used to mitigate inflammation, although treatment is approached cautiously due to potential side effects. Despite advances in diagnostic methods and treatment options, a subset of patients may experience persistent symptoms or complications that can be severe. Understanding sarcoidosis is crucial for managing its impact on health and improving patient outcomes.
Sarcoidosis
ALSO KNOWN AS: Besnier-Boeck disease, Schaumann’s syndrome, Lofgren syndrome (acute sarcoidosis)
ANATOMY OR SYSTEM AFFECTED: Brain, chest, circulatory system, eyes, heart, immune system, joints, kidneys, lungs, lymphatic system, nerves, nervous system, respiratory system, skin, spleen
DEFINITION: An inflammatory disease of unknown cause characterized by noncaseating granulomas that affect multiple systems, especially the lungs, lymph nodes, skin, and eyes. This disease is thought to be the result of a dysregulated immune response to an infectious agent or environmental factor. If severe, sarcoidosis is treated with corticosteroids.
CAUSES: Unknown; dysregulated immune system response to pathogen or environmental toxin
SYMPTOMS: Fatigue, cough, inflammation, granulomas
DURATION: Years; may resolve without treatment or persist
TREATMENTS: Corticosteroids
Causes and Symptoms
Sarcoidosis, an inflammatory disease of unknown cause, affects multiple organs and systems in the body. Most commonly affected are the lungs, lymph nodes, skin, and eyes. Other organs and systems that can be involved include the liver, spleen, bone, joints, heart, muscle, and central nervous system. Sarcoidosis is thought to be the result of an unusual immune reaction to an environmental antigen, such as a bacterium, fungus, or environmental toxin. Sarcoidosis is characterized by the presence of noncaseating granulomas in the affected tissues. These granulomas are ball-shaped clusters of immune cells consisting of macrophage and epitheloid cells encircled by lymphocytes. A granuloma begins when certain types of lymphocytes interact with antigen-presenting cells. Macrophages that have engulfed antigens are chronically stimulated by cytokines, differentiate into epitheliod cells, and fuse to form multinucleated giant cells. If a granuloma persists for an extended period of time, then fibroblasts and collagen encase the ball of cells. This eventually leads to fibrosis, or permanent scarring, which can lead to organ impairment.
The incidence of sarcoidosis varies greatly by ethnic group, indicating a genetic component to the disease. In the United States, 40 in 100,000 African Americans develop sarcoidosis, compared to 5 in 100,000 Caucasians. In Sweden, the incidence is 64 in 100,000. In general, more women develop sarcoidois than men. Sarcoidosis can occur at any age, but the average age at detection is between twenty and forty years.
The initial symptoms of sarcoidosis may include coughs, wheezing, chest discomfort, night chills, and weight loss. Many patients learn that they have sarcoidosis when a routine chest x-ray shows abnormalities. Most if not all of the symptoms of sarcoidosis are not unique to the disease, so diagnosis involves ruling out other conditions, such as an infection. Typical first signs of sarcoidosis include skin lesions, problems with the lungs (such as decreased lung function), and enlarged lymph nodes. A bronchoscopy may be performed to inspect the bronchial tubes and to obtain a tissue for biopsy. A positive biopsy would reveal a large number of white blood cells, general inflammation, and the presence of granulomas. Gallium-67 scans may be used; in these scans, the radioactive element gallium-67 is injected and accumulates in areas of inflammation, infection, or rapid cell division. More recently, the more sensitive fludeoxyglucose–positron emission tomography (FDG-PET) scan, which uses the radioactive sugar fludeoxyglucose (18F) (FDG) instead of gallium, is increasingly being used. Patients with sarcoidosis in the eyes have redness in the eyes, photophobia, and blurred vision.
Treatment and Therapy
An estimated 60 to 70 percent of cases of sarcoidosis will resolve within one to two years. For severe sarcoidosis, corticosteroids, such as prednisone, are given to reduce inflammation. Since steroids can have severe side effects, treatment may not be given unless organs are impaired. Some 20 to 30 percent of patients will develop a chronic condition of persistent sarcoidosis that damages organs as a result of fibrosis. It is estimated that in 5 to 10 percent of patients, sarcoidosis will be the cause of death, usually from lung fibrosis resulting in respiratory failure or from cardiac or neurological complications.
Perspective and Prospects
The skin lesions of sarcoidosis were first recognized in 1869 by English dermatologist Jonathan Hutchinson. In 1897, Caesar Boeck independently described the skin lesions using the term “sarcoidosis,” meaning “fleshlike condition.” The multiple system involvement was recognized by Jörgen Schaumann in 1915, the same time that Alexander Bittorf described lung lesions of the condition. In 1941, Morten A. Kveim, a Norwegian physician, developed a test for sarcoidosis that involved injecting lymph-node tissue from a confirmed sarcoidois patient into the skin of a person suspected of having sarcoidosis. If granulomas developed at the injection site four to six weeks later, then the patient was positive for sarcoidosis. In 1954, Louis Siltzbach modified the test to use tissue from a sarcoidosis patient's spleen. If the patient was receiving steroid treatment, then the granulomas might not develop, leading to a false negative on the test. The Kveim test is no longer used to diagnose sarcoidosis, largely because of the lack of commercially available Kveim reagent and its replacement by other diagnostic methods, such as bronchoscopy. A promising development in the treatment of extensive sarcoidosis is the use of FDG-PET, which is more sensitive than the conventional gallium method, to monitor a patient’s response to drug therapy. Research into the genetics of sarcoidosis indicates likely multiple genetic factors. A predisposition to developing sarcoidosis is associated with HLA-DQ and HLA-DR genes.
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