Sarcoidosis

Cause

The exact cause of sarcoidosis is not known. The current working hypothesis is, in genetically susceptible individuals, sarcoidosis is caused through alteration to the immune response after exposure to an environmental, occupational, or infectious agent. Some cases may be caused by treatment with tumor necrosis factor (TNF) inhibitors like etanercept.

Genetics

The heritability of sarcoidosis varies according to ethnicity. About 20% of African Americans with sarcoidosis have a family member with the condition, whereas the same figure for European Americans is about 5%. Additionally, in African Americans, who seem to experience more severe and chronic disease, siblings and parents of sarcoidosis cases have about a 2.5-fold increased risk for developing the disease. In Swedish individuals heritability was found to be 39%. In this group, if a first-degree family member was affected, a person has a four-fold greater risk of being affected.

Investigations of genetic susceptibility yielded many candidate genes, but only a few were confirmed by further investigations, and no reliable genetic markers are known. Currently, the most interesting candidate gene is BTNL2; several HLA-DR risk alleles are also being investigated. In persistent sarcoidosis, the HLA haplotype HLA-B7-DR15 is either cooperating in disease or another gene between these two loci is associated. In nonpersistent disease, a strong genetic association exists with HLA DR3-DQ2. Cardiac sarcoid has been connected to tumor necrosis factor alpha (TNFA) variants.

Infectious agents

Several infectious agents appear to be significantly associated with sarcoidosis, but none of the known associations is specific enough to suggest a direct causative role. The major implicated infectious agents include: mycobacteria, fungi, borrelia, and rickettsia. A meta-analysis investigating the role of mycobacteria in sarcoidosis found it was present in 26.4% of cases, but they also detected a possible publication bias, so the results need further confirmation. Mycobacterium tuberculosis catalase-peroxidase has been identified as a possible antigen catalyst of sarcoidosis. The disease has also been reported by transmission via organ transplants. A large epidemiological study found little evidence that infectious diseases spanning years before sarcoidosis diagnosis could confer measurable risks for sarcoidosis diagnosis in the future.

Autoimmune

An association with autoimmune disorders has been frequently observed. The exact mechanism of this relation is not known, but some evidence supports the hypothesis that it is a consequence of Th1 lymphokine prevalence. Tests of delayed cutaneous hypersensitivity have been used to measure progression.

Pathophysiology

Granulomatous inflammation is characterized primarily by the accumulation of macrophages and activated T-lymphocytes, with increased production of key inflammatory mediators, tumor necrosis factor alpha (TNF), interferon gamma, interleukin 2 (IL-2), IL-8, IL-10, IL-12, IL-18, IL-23 and transforming growth factor beta (TGF-β), indicative of a T helper cell-mediated immune response. Sarcoidosis has paradoxical effects on inflammatory processes; it is characterized by increased macrophage and CD4 helper T-cell activation, resulting in accelerated inflammation, but immune response to antigen challenges such as tuberculin is suppressed. This paradoxical state of simultaneous hyper- and hypoactivity is suggestive of a state of anergy. The anergy may also be responsible for the increased risk of infections and cancer. The regulatory T-lymphocytes in the periphery of sarcoid granulomas appear to suppress IL-2 secretion, which is hypothesized to cause the state of anergy by preventing antigen-specific memory responses.

While TNF is widely believed to play an important role in the formation of granulomas (this is further supported by the finding that in animal models of mycobacterial granuloma formation inhibition of either TNF or IFN-γ production inhibits granuloma formation), sarcoidosis can and does still develop in those being treated with TNF antagonists like etanercept. B cells also likely play a role in the pathophysiology of sarcoidosis. Serum levels of soluble human leukocyte antigen (HLA) class I antigens and angiotensin converting enzyme (ACE) are higher in people with sarcoidosis. Likewise, the ratio of CD4/CD8 T cells in bronchoalveolar lavage is usually higher in people with pulmonary sarcoidosis (usually >3.5), although it can be normal or even abnormally low in some cases. Serum ACE levels have been found to usually correlate with total granuloma load.

Cases of sarcoidosis have also been reported as part of the immune reconstitution syndrome of HIV, that is, when people receive treatment for HIV, their immune system rebounds. The result is that it begins to attack the antigens of opportunistic infections caught before said rebound, and the resulting immune response damages healthy tissue.

Histopathology

Sarcoidosis is characterized by the formation of non-necrotizing ("non-caseating") granulomas in various organs and tissues. Giant cells, specifically Langhans giant cells, are often seen in sarcoidosis. Schaumann bodies seen in sarcoidosis are calcium and protein inclusions inside of giant cells as part of a granuloma. Asteroid bodies can be seen in sarcoidosis. Hamazaki–Wesenberg bodies can be seen in lymph nodes and more rarely in lung biopsies with sarcoidosis and are inclusion bodies of lysosomes with protein, glycoprotein and iron.

Diagnosis

Diagnosis of sarcoidosis is a diagnosis of exclusion, as there is no specific test for the condition other than the Kveim-Siltzbach test. To exclude sarcoidosis in a case presenting with pulmonary symptoms might involve a chest radiograph, CT scan of chest, PET scan, CT-guided biopsy, mediastinoscopy, open lung biopsy, bronchoscopy with biopsy, endobronchial ultrasound, and endoscopic ultrasound with fine-needle aspiration of mediastinal lymph nodes (EBUS FNA). Tissue from biopsy of lymph nodes is subjected to both flow cytometry to rule out cancer and special stains (acid fast bacilli stain and Gömöri methenamine silver stain) to rule out microorganisms and fungi.

Serum markers of sarcoidosis include: serum amyloid A, soluble interleukin-2 receptor, lysozyme, angiotensin converting enzyme, and the glycoprotein KL-6. Angiotensin-converting enzyme blood levels are used in the monitoring of sarcoidosis. A bronchoalveolar lavage can show an elevated (of at least 3.5) CD4/CD8 T cell ratio, which is indicative (but not proof) of pulmonary sarcoidosis. In at least one study, the induced sputum ratio of CD4/CD8 and the level of TNF were correlated to those in the lavage fluid. A sarcoidosis-like lung disease called granulomatous–lymphocytic interstitial lung disease can be seen in patients with common variable immunodeficiency (CVID) and therefore serum antibody levels should be measured to exclude CVID.

Differential diagnosis includes metastatic disease, lymphoma, septic emboli, rheumatoid nodules, granulomatosis with polyangiitis, varicella infection, tuberculosis, and atypical infections, such as Mycobacterium avium complex, cytomegalovirus, and cryptococcus. Sarcoidosis is confused most commonly with neoplastic diseases, such as lymphoma, or with disorders characterized also by a mononuclear cell granulomatous inflammatory process, such as the mycobacterial and fungal disorders.

Chest radiograph changes are divided into four stages:

1. bihilar lymphadenopathy
2. bihilar lymphadenopathy and reticulonodular infiltrates
3. bilateral pulmonary infiltrates
4. fibrocystic sarcoidosis, typically with upward hilar retraction, cystic and bullous changes

Although people with stage 1 radiographs tend to have the acute or subacute, reversible form of the disease, those with stages 2 and 3 often have the chronic, progressive disease; these patterns do not represent consecutive "stages" of sarcoidosis. Thus, except for epidemiologic purposes, this categorization is mostly of historic interest.

In sarcoidosis presenting in the Caucasian population, hilar adenopathy and erythema nodosum are the most common initial symptoms. In this population, a biopsy of the gastrocnemius muscle is a useful tool in correctly diagnosing the person. The presence of a noncaseating epithelioid granuloma in a gastrocnemius specimen is definitive evidence of sarcoidosis, as other tuberculoid and fungal diseases extremely rarely present histologically in this muscle.

Cardiac magnetic resonance imaging (CMR) is one modality for diagnosing cardiac sarcoidosis. It has 78% specificity in diagnosing cardiac sarcoidosis. Its T2-weighted imaging can detect acute inflammation. Meanwhile, late gadolinium contrast (LGE) can detect fibrosis or scar. Lesions at the subpericardium and midwall enhancement of the basal septum or inferolateral wall are strongly suggestive of sarcoidosis. MRI can also follow up on the treatment efficacy of corticosteroids and prognosis of cardiac sarcoidosis.

PET scan can quantify disease activity, which cannot be performed by CMR.

Classification

Sarcoidosis may be divided into the following types:

• Annular sarcoidosis
• Erythrodermic sarcoidosis
• Ichthyosiform sarcoidosis
• Hypopigmented sarcoidosis
• Löfgren syndrome
• Lupus pernio
• Morpheaform sarcoidosis
• Mucosal sarcoidosis
• Neurosarcoidosis
• Papular sarcoid
• Scar sarcoid
• Subcutaneous sarcoidosis
• Systemic sarcoidosis
• Ulcerative sarcoidosis

Treatment

Treatments for sarcoidosis vary greatly depending on the patient. At least half of patients require no systemic therapy. Most people (>75%) only require symptomatic treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin. For those presenting with lung symptoms, unless the respiratory impairment is devastating, active pulmonary sarcoidosis is observed usually without therapy for two to three months; if the inflammation does not subside spontaneously, therapy is instituted.

Major categories of drug interventions include glucocorticoids, antimetabolites, biologic agents, especially monoclonal anti-tumor necrosis factor antibodies. Investigational treatments include specific antibiotic combinations and mesenchymal stem cells. If drug intervention is indicated, a step-wise approach is often used to explore alternatives in order of increasing side effects and to monitor potentially toxic effects.

Corticosteroids, most commonly prednisone or prednisolone, have been the standard treatment for many years. In some people, this treatment can slow or reverse the course of the disease, but other people do not respond to steroid therapy. The use of corticosteroids in mild disease is controversial because, in many cases, the disease remits spontaneously.

Antimetabolites

Antimetabolites, also categorized as steroid-sparing agents, such as azathioprine, methotrexate, mycophenolic acid, and leflunomide are often used as alternatives to corticosteroids. Of these, methotrexate is most widely used and studied. Methotrexate is considered a first-line treatment in neurosarcoidosis, often in conjunction with corticosteroids. Long-term treatment with methotrexate is associated with liver damage in about 10% of people and hence may be a significant concern in people with liver involvement and requires regular liver function test monitoring. Methotrexate can also lead to pulmonary toxicity (lung damage), although this is fairly uncommon and more commonly it can confound the leukopenia caused by sarcoidosis. Due to these safety concerns it is often recommended that methotrexate is combined with folic acid in order to prevent toxicity. Azathioprine treatment can also lead to liver damage. However, the risk of infection appears to be about 40% lower in those treated with methotrexate instead of azathioprine. Leflunomide is being used as a replacement for methotrexate, possibly due to its purportedly lower rate of pulmonary toxicity. Mycophenolic acid has been used successfully in uveal sarcoidosis, neurosarcoidosis (especially CNS sarcoidosis; minimally effective in sarcoidosis myopathy), and pulmonary sarcoidosis.

Immunosuppressants

As the granulomas are caused by collections of immune system cells, particularly T cells, there has been some success using immunosuppressants (like cyclophosphamide, cladribine, chlorambucil, and cyclosporine), immunomodulatory (pentoxifylline and thalidomide), and anti-tumor necrosis factor treatment (such as infliximab, etanercept, golimumab, and adalimumab).

In a clinical trial, cyclosporine added to prednisone treatment failed to demonstrate any significant benefit over prednisone alone in people with pulmonary sarcoidosis. There was evidence of increased toxicity from the addition of cyclosporine to the steroid treatment, including infections, malignancies (cancers), hypertension, and kidney dysfunction. Likewise chlorambucil and cyclophosphamide are seldom used in the treatment of sarcoidosis due to their high degree of toxicity, especially their potential for causing malignancies. Infliximab has been used successfully to treat pulmonary sarcoidosis in clinical trials in several cases. Etanercept, on the other hand, has failed to demonstrate any significant efficacy in people with uveal sarcoidosis in a couple of clinical trials. Likewise, golimumab has failed to show any benefit in those with pulmonary sarcoidosis. One clinical trial of adalimumab found treatment response in about half of subjects, which is similar to that seen with infliximab. Adalimumab has a better tolerability profile; it may be preferred over infliximab.

Specific organ treatments

Ursodeoxycholic acid has been used successfully as a treatment for cases with liver involvement. Thalidomide has also been tried successfully as a treatment for treatment-resistant lupus pernio in a clinical trial, which may stem from its anti-TNF activity. It failed to exhibit any efficacy in a pulmonary sarcoidosis clinical trial. Cutaneous disease may be successfully managed with antimalarials (such as chloroquine and hydroxychloroquine) and the tetracycline antibiotic, minocycline. Antimalarials have also demonstrated efficacy in treating sarcoidosis-induced hypercalcemia and neurosarcoidosis. Long-term use of antimalarials is limited, however, by their potential to cause irreversible blindness and hence the need for regular ophthalmologic screening. This toxicity is usually less of a problem with hydroxychloroquine than with chloroquine, although hydroxychloroquine can disturb the glucose homeostasis.

Recently selective phosphodiesterase 4 (PDE4) inhibitors like apremilast (a thalidomide derivative), roflumilast, and the less subtype-selective PDE4 inhibitor, pentoxifylline, have been tried as a treatment for sarcoidosis, with successful results being obtained with apremilast in cutaneous sarcoidosis in a small open-label study. Pentoxifylline has been used successfully to treat acute disease although its use is greatly limited by its gastrointestinal toxicity (mostly nausea, vomiting, and diarrhea). Case reports have supported the efficacy of rituximab, an anti-CD20 monoclonal antibody and a clinical trial investigating atorvastatin as a treatment for sarcoidosis is under-way. ACE inhibitors have been reported to cause remission in cutaneous sarcoidosis and improvement in pulmonary sarcoidosis, including improvement in pulmonary function, remodeling of lung parenchyma and prevention of pulmonary fibrosis in separate case series'. Nicotine patches have been found to possess anti-inflammatory effects in sarcoidosis patients, although whether they had disease-modifying effects requires further investigation. Antimycobacterial treatment (drugs that kill off mycobacteria, the causative agents behind tuberculosis and leprosy) has also proven itself effective in treating chronic cutaneous (that is, it affects the skin) sarcoidosis in one clinical trial. Quercetin has also been tried as a treatment for pulmonary sarcoidosis with some early success in one small trial.

Because of its uncommon nature, the treatment of male reproductive tract sarcoidosis is controversial. Since the differential diagnosis includes testicular cancer, some recommend orchiectomy, even if evidence of sarcoidosis in other organs is present. In the newer approach, testicular, epididymal biopsy, and resection of the largest lesion have been proposed.

Symptoms

People with sarcoidosis may have a range of symptoms that do not correspond with objective physical evidence of disease, but that still decrease quality of life.

Physical therapy, rehabilitation, and counseling can help avoid deconditioning, and improve social participation, psychological well-being, and activity levels. Key aspects are avoiding exercise intolerance and muscle weakness.

Low or moderate-intensity physical training has been shown to improve fatigue, psychological health, and physical functioning in people with sarcoidosis without adverse effects. Inspiratory muscle training has also decreased severe fatigue perception in subjects with early stages of sarcoidosis, as well as improving functional and maximal exercise capacity and respiratory muscle strength. The duration, frequency, and physical intensity of exercise needs to accommodate impairments such as joint pain, muscle pain, and fatigue.

Neurostimulants such as methylphenidate and modafinil have shown some effectiveness as an adjunct for the treatment of sarcoidosis fatigue.

Treatments for symptomatic neuropathic pain in sarcoidosis patients are similar to those for other causes, and include antidepressants, anticonvulsants, and prolonged-release opioids; however, only 30 to 60% of patients experience limited pain relief.

Prognosis

The disease can remit spontaneously or become chronic, with exacerbations and remissions. In some cases, it can progress to pulmonary fibrosis and death. In benign cases, remission can occur in 24 to 36 months without treatment, but regular follow-ups are required. In some cases, however, the condition may persist for several decades. Two-thirds of people with the condition achieve a remission within 10 years of the diagnosis. When the heart is involved, the prognosis is generally less favourable, though corticosteroids appear effective in improving AV conduction. The prognosis tends to be less favourable in African Americans than in white Americans. In a Swedish population-based analysis, the majority of cases who did not have severe disease at diagnosis had comparable mortality to the general population. The risk for premature death was markedly (2.3-fold) increased compared to the general population for a smaller group of cases with severe disease at diagnosis. Serious infections, sometimes multiple during the course of disease, and heart failure might contribute to the higher risk of early death in some patients with sarcoidosis.

Some 1990s studies indicated that people with sarcoidosis appear to be at significantly increased risk for cancer, in particular lung cancer, lymphomas, and cancer in other organs known to be affected in sarcoidosis. In sarcoidosis-lymphoma syndrome, sarcoidosis is followed by the development of a lymphoproliferative disorder such as non-Hodgkin lymphoma. This may be attributed to the underlying immunological abnormalities that occur during the sarcoidosis disease process. Sarcoidosis can also follow cancer or occur concurrently with cancer. There have been reports of hairy cell leukemia, acute myeloid leukemia, and acute myeloblastic leukemia associated with sarcoidosis. Sometimes, sarcoidosis, even untreated, can be complicated by opportunistic infections although these are rare.

Epidemiology

Sarcoidosis most commonly affects young adults of both sexes, although studies have reported more cases in females. Incidence is highest for individuals younger than 40 and peaks in the age group from 20 to 29 years; a second peak is observed for women over 50.

Sarcoidosis occurs throughout the world in all races, with an average incidence of 16.5 per 100,000 in men and 19 per 100,000 in women. The disease is most common in Northern European countries, and the highest annual incidence of 60 per 100,000 is found in Sweden and Iceland. In the United Kingdom, the prevalence is 16 in 100,000. In the United States, sarcoidosis is more common in people of African descent than Caucasians, with annual incidence reported as 35.5 and 10.9 per 100,000, respectively. Sarcoidosis is less commonly reported in South America, Spain, India, Canada, and the Philippines. There may be a higher susceptibility to sarcoidosis in those with celiac disease. An association between the two disorders has been suggested.

There has also been a seasonal clustering observed in sarcoidosis-affected individuals. In Greece about 70% of diagnoses occur between March and May every year, in Spain about 50% of diagnoses occur between April and June, and in Japan it is mostly diagnosed during June and July.

The differing incidence across the world may be at least partially attributable to the lack of screening programs in certain regions of the world, and the overshadowing presence of other granulomatous diseases, such as tuberculosis, that may interfere with the diagnosis of sarcoidosis where they are prevalent. There may also be differences in the severity of the disease between people of different ethnicities. Several studies suggest the presentation in people of African origin may be more severe and disseminated than for Caucasians, who are more likely to have asymptomatic disease. Manifestation appears to be slightly different according to race and sex. Erythema nodosum is far more common in men than in women and in Caucasians than in other races. In Japanese people, ophthalmologic and cardiac involvement are more common than in other races.

It is more common in certain occupations, namely firefighters, educators, military personnel, those who work in industries where pesticides are used, law enforcement, and healthcare personnel. In the year after the September 11 attacks, the rate of sarcoidosis incidence went up fourfold (to 86 cases per 100,000).

History

It was first described in 1877 by Dr. Jonathan Hutchinson, a dermatologist, as a condition causing red, raised rashes on the face, arms, and hands. In 1889 the term lupus pernio was coined by Dr. Ernest Besnier, another dermatologist. Later in 1892 lupus pernio's histology was defined. In 1902, bone involvement was first described by a group of three doctors. Between 1909 and 1910, uveitis in sarcoidosis was first described, and later in 1915, it was emphasised by Dr. Jörgen Nielsen Schaumann that it was a systemic condition. This same year, lung involvement was also described. In 1937 uveoparotid fever was first described and likewise in 1941 Löfgren syndrome was first described. In 1958 the first international conference on sarcoidosis was called in London, likewise the first USA sarcoidosis conference occurred in Washington, D.C., in the year 1961. It has also been called Besnier–Boeck disease or Besnier–Boeck–Schaumann disease.

Etymology

The word "sarcoidosis" comes from Greek [σάρκο-] sarco- meaning "flesh", the suffix -(e)ido (from the Greek εἶδος -eidos [usually omitting the initial e in English as the diphthong epsilon-iota in Classic Greek stands for a long "i" = English ee]) meaning "type", " resembles" or "like", and -sis, a common suffix in Greek meaning "condition". Thus, the whole word means "a condition that resembles crude flesh". The first cases of sarcoïdosis, which were recognised as a new pathological entity in Scandinavia at the end of the 19th century, exhibited skin nodules resembling cutaneous sarcomas, hence the name initially given.

Society and culture

The World Association of Sarcoidosis and Other Granulomatous Disorders (WASOG) is an organisation of physicians involved in the diagnosis and treatment of sarcoidosis and related conditions. WASOG publishes the journal Sarcoidosis, Vasculitis and Diffuse Lung Diseases. Additionally, the Foundation for Sarcoidosis Research (FSR) is devoted to supporting research into sarcoidosis and its possible treatments.

There have been concerns that World Trade Center rescue workers are at a heightened risk for sarcoidosis.

Comedian and actor Bernie Mac had sarcoidosis. In 2005, he mentioned that the disease was in remission. His death on August 9, 2008, was caused by complications from pneumonia, though Mac's agent states the sarcoidosis was not related to his fatal pneumonia.

Karen "Duff" Duffy, MTV personality and actress, was diagnosed with neurosarcoidosis in 1995.

American football player Reggie White died in 2004, with pulmonary and cardiac sarcoidosis being contributing factors to his fatal heart arrhythmia.

Singer Sean Levert died in 2008 of sarcoidosis complications.

Manning Marable, a professor of public policy at Columbia University, died of pneumonia in 2011, less than a year after undergoing a double lung transplant following a diagnosis of sarcoidosis. In 2012, he was posthumously awarded a Pulitzer Prize in history for his biography "Malcolm X: A Life of Reinvention."

Joseph Rago, Pulitzer Prize-winning writer known for his work at The Wall Street Journal, died of sarcoidosis complications in 2017.

The late American chess grandmaster Daniel Naroditsky had systemic sarcoidosis, and it was reported that the disease was the underlying cause of the cardiac arrhythmia that led to his death in 2025.

Several historical figures are suspected of having sarcoidosis. In a 2014 letter to the British medical journal The Lancet, it was suggested that the French Revolution leader Maximilien Robespierre may have had sarcoidosis, causing him impairment during his time as head of the Reign of Terror. The symptoms associated with Ludwig van Beethoven's 1827 death have been described as possibly consistent with sarcoidosis. Author Robert Louis Stevenson (1850–1894) had a history of chronic coughs and chest complaints, and sarcoidosis has been suggested as a diagnosis.

Pregnancy

Sarcoidosis generally does not prevent successful pregnancy and delivery; the increase in estrogen levels during pregnancy may even have a slightly beneficial immunomodulatory effect. In most cases, the course of the disease is unaffected by pregnancy, with improvement in a few cases and worsening of symptoms in very few cases, although a number of the immunosuppressants (such as methotrexate, cyclophosphamide) used in corticosteroid-refractory sarcoidosis are known teratogens. Increased risks associated with sarcoidosis, ranging from 30 to 70%, have been reported for preeclampsia/eclampsia, cesarian or preterm delivery, as well as (non-cardiac) birth defects in first singleton pregnancies. In absolute numbers, birth defects and other complications such as maternal death, cardiac arrest, placental abruption or venous thromboembolism are extremely rare in sarcoidosis pregnancies.