Sarcoidosis
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Sarcoidosis is an uncommon autoimmune disorder of unknown cause. The disease is characterised by the presence of microscopic non-necrotising granulomas (small inflammatory nodules) which can appear almost anywhere in the body. In many patients granulomas appear in the lungs or the lymph nodes. Symptoms can occasionally appear suddenly but more often than not appear gradually. When viewing X-rays of the lungs, sarcoidosis can have the appearance of tuberculosis or lymphoma.
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Epidemiology
Sarcoidosis occurs throughout the world in any race. It is more commonly seen in blacks than whites, primarily people of northern European descent in the latter case. Pulmonary involvement is the most common presentation of sarcoidosis.
Signs and symptoms
Sarcoidosis is a systemic disease that can affect any organ. Common symptoms are vague, such as fatigue unchanged by sleep, lack of energy, aches and pains, dry eyes, blurry vision, shortness of breath, a dry hacking cough or skin lesions. The cutaneous symptoms are protean, and range from rashes and noduli (small bumps) to erythema nodosum or lupus pernio.
Renal, liver, heart or brain involvement may cause further symptoms and altered functioning. Manifestations in the eye include uveitis and retinal inflammation, which may result in loss of visual acuity or blindness. Sarcoidosis affecting the brain or nerves is known as neurosarcoidosis.
Hypercalcemia (high calcium levels) and its symptoms may be the result of excessive vitamin D production.
Sarcoidosis most often manifests as a restrictive disease of the lungs, causing a decrease in lung volume and decreased compliance (the ability to stretch). The vital capacity (full breath in, to full breath out) is decreased, and most of this air can be blown out in the first second. This means the FEV1/FVC ratio is increased from the normal of about 80%, to 90%.
Causes and pathophysiology
No direct cause of sarcoidosis has been identified, although it there have been reports of cell wall deficient bacteria that may be possible pathogensTemplate:Ref. These bacteria are not identified in standard laboratory analysis. It has been thought that there may be a hereditary factor because some families have multiple members with sarcoidosis. To date, no reliable genetic markers have been identified, and an alternate hypotheses is that family members share similar exposures to environmental pathogens. There have also been reports of transmission of sarcoidosis via organ transplantsTemplate:Ref.
Sarcoidosis frequently causes a dysregulation of vitamin D production; extrarenal (outside the kidney) production can be marked. Production of vitamin D goes on outside the kidneysTemplate:Ref. This results in elevated levels of the hormone 1,25-dihydroxyvitamin D and symptoms of hypervitaminosis D that may include fatigue, lack of strength or energy, irritability, metallic taste, temporary memory loss or cognitive problems. Physiological compensatory responses (e.g. suppression of the parathyroid hormone levels) may mean the patient does not develop frank hypercalcemia.
Treatment
Corticosteroids, most commonly prednisone, have been the standard treatment for many years, although they are only reliable for symptom relief. The use of corticosteroids in mild disease has been the subject of mounting doubt, because corticoteroids have recognized dose-and duration-related side effects, and their use has been linked to relapses and worsening of the diseaseTemplate:Ref.
Severe symptoms have generally been treated with steroids, and later with steroid-sparing agents. As the granulomas are caused by collections of immune system cells, particularly T cells, there has been some early indications of success using immunosuppressants, interleukin-2 inhibitors or anti-tumor necrosis factor treatment (such as infliximab). Unfortunately, none of these have provided reliable treatment and there can be signficant side effects.
Disciplined avoidance of sunlight and vitamin D foods is necessary in patients who are prone to develop hypercalcemia and will help relieve symptoms in all sarcoidosis patients.
Antibiotic therapy has been reported to be effective for lung, lymph and cutaneous manifestations of sarcoidosisTemplate:Ref Template:Ref.
References
- Template:Note Almenoff PL, Johnson A, Lesser M, Mattman LH. Growth of acid fast L forms from the blood of patients with sarcoidosis. Thorax 1996;51:530-3. PMID 8711683.
- Template:Note Padilla ML, Schilero GJ, Teirstein AS. Donor-acquired sarcoidosis. Sarcoidosis Vasc Diffuse Lung Dis 2002;19:18-24. PMID 12002380.
- Template:Note Barbour GL, Coburn JW, Slatopolsky E, Norman AW, Horst RL. Hypercalcemia in an anephric patient with sarcoidosis: evidence for extrarenal generation of 1,25-dihydroxyvitamin D. N Engl J Med 1981;305:440-3. PMID 6894783.
- Template:Note Gottlieb JE, Israel HL, Steiner RM, Triolo J, Patrick H. Outcome in sarcoidosis. The relationship of relapse to corticosteroid therapy. Chest 1997;111:623-31. PDF (http://www.chestjournal.org/cgi/reprint/111/3/623.pdf). PMID 9118698.
- Template:Note Bachelez H, Senet P, Cadranel J, Kaoukhov A, Dubertret L. The use of tetracyclines for the treatment of sarcoidosis. Arch Dermatol 2001;137:69-73. PMID 11176663.
- Template:Note Marshall TG, Marshall FE. Sarcoidosis succumbs to antibiotics--implications for autoimmune disease. Autoimmun Rev 2004;3:295-300. PMID 15246025.
External links
- Microscopy of granulomas in sarcoidosis (http://155.37.5.42/eAtlas/RESP/1654b.htm)de:Sarkoidose