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Sarcoidosis is a multisystem disorder and, although predominantly respiratory (>90%), many tissues can be affected (see below). It usually presents in young adults, 20-40 years old, and is most frequent in Afro-Caribbeans, Scandinavians, the Irish and relatives of patients with sarcoidosis. Black people are more susceptible to aggressive, systemic disease. Incidence varies geographically from 5 to 00/ 05 population.

Aetiology: unknown, but it often follows exposure of a genetically susceptible person (e.g. HLA-DR) to an antigenic trigger which may be infective (e.g. mycobacteria and propionibacteria), geographical (e.g. pine pollen) or occupational (e.g. beryllium and talc). Autoimmune causes are less likely. Histopathology is characterized by non- caseating granulomata (NCG) and an abnormal, antigen-triggered CD4 (helper) T-cell response. Interferon-γ release stimulates granuloma formation, fibroblast and fibrosis. Activated macrophages release serum angiotensin-converting enzyme (SACE), and B-cell stimulation produces immunoglobulin and immune complex formation. Delayed hypersensitivity (e.g. to tuberculin) is reduced due to T-cell migration. Figure 3 a illustrates other causes of lung granuloma.
Sarcoidosis, Pulmonary sarcoidosis, Acute sarcoidosis, Pulmonary function tests, Steroid therapy, Immunosuppressive therapy, Lung transplant, Extrathoracic disease, Cardiac disease, Neurosarcoid

Clinical features: pulmonary (>90%), systemic or both:
1 Pulmonary sarcoidosis may be asymptomatic ( 30%) or associated with constitutional (e.g. fever, malaise, weight loss 30% and fatigue 70%) and/or respiratory (e.g. non-productive cough, dyspnoea and chest discomfort 30-50%) symptoms. Physical finding (e.g. club- bing) are rare and despite CXR infiltrate crepitations occur in less than 20% of cases. There are two distinct pulmonary presentations:
(a) Acute sarcoidosis (Lo·fgren's syndrome) occurs mainly in Caucasians with fever, erythema nodosum (EN), arthralgia, pulmonary infiltrate and bihilar lymphadenopathy (BHL; Fig. 3 c(i)). The CXR f ndings may be asymptomatic. Exclude other causes of BHL (Fig. 3 b). About 0% develop progressive lung fibrosi (Fig. 3 c).
(b) Progressive, interstitial lung disease causes increasing dyspnoea and cough. Infiltrate ( +BHL) are seen on CXR (Fig. 3 c(iii)) and may progress to lung fibrosi and respiratory failure.
Diagnosis: requires a compatible clinical (+CXR) picture-histological confirmatio of NCG and exclusion of other causes (e.g. TB). Figure 3 d summarizes evaluation. Disease progression is monitored by serial clinical assessment, CXR, spirometry ( +DLco) and SACE.
SACE is raised in 80% of acute sarcoidosis and is suppressed by steroids. It aids monitoring but is not specifi (i.e. raised in TB).
CXR is abnormal in more than 85% of lung sarcoid, but 30-60% are asymptomatic (i.e. incidental CXR finding) BHL occurs in 50-85%, unilateral hilar lymphadenopathy in < 0% and pulmonary infiltrates usually central or in the upper lobes, in 25-50% of cases (Fig. 3 c). Figure 3 e shows the CXR staging system.
High-resolution CT scans are not required for routine evaluation. They are useful if the CXR is normal, to discriminate between inflammatio and fibrosi and to detect complications. Characteristic early features include bronchovascular micronodules (Fig. 3 f), inflammatio with ground glass opacificatio and septal thickening. Later disease causes traction bronchiectasis and f brosis.
Histological confirmation is not always needed in asymptomatic or acute disease but is recommended in symptomatic cases or if BHL is asymmetrical or massive to exclude malignancy ( 0%). Transbronchial lung biopsies histologically confir approximately 70% of cases. Bronchoalveolar lavage CD4:CD8 ratio of more than 3.5 is also specifi for sarcoidosis. Tissue biopsies (e.g. skin and salivary/parotid gland) also confir the diagnosis, but liver biopsies are not specific A positive Mantoux test makes sarcoidosis unlikely.
Pulmonary function tests (PFTs) are abnormal in 20% of stage I and 40-70% of stage II-IV radiographic disease (Fig. 3 e). Typically, the defect is restrictive, but obstructive lesions occur in approximately 40% of cases. Gas transfer (DLco) and FVC are reduced despite a normal CXR in 5-50% of cases.
Management: Most pulmonary sarcoidosis resolves spontaneously and treatment is not required (Fig. 3 e). Asymptomatic BHL and CXR infiltrate (stage II and III) should be monitored.
a.  Steroid therapy alleviates acute symptoms but does not prevent progressive pulmonary fibrosis Figure 3 g summarizes indications for treatment. The initial response to high-dose steroids (e.g. pred- nisolone 30-60 mg daily) is evaluated after -2 months and gradually tapered over 6-24 months. Relapse is common (>33% within 2 years) and is managed with prolonged low-dose steroid therapy. Prophylaxis against osteoporosis and peptic ulcers is required. Inhaled steroids have a limited role.
b.  Immunosuppressive therapy is indicated for steroid-insensitive disease and as steroid sparing agents. Methotrexate and azothioprine are beneficia in approximately 50% of steroid-resistant cases. Other cytotoxic agents include cyclophosphamide and cyclosporine. All cause toxicity and must be monitored. Hydroxychloroquine inhibits macrophage TNF-α production and granuloma formation. It is effective for hypercalcaemia, skin, lung and neurosarcoid.
c.   Lung transplant is considered in end-stage lung disease. NCG may recur in transplanted lung.

2 Extrathoracic disease is associated with fever, weight loss, malaise and arthralgia. Other features include hepatic NCG (60%), renal impairment (35%), splenomegaly, bone cysts and parotid, lacrimal or salivary gland swelling. Hypercalcaemia is common in men and Caucasians.
a.    Skin is often affected in women ( 25%). EN describes painful, inflame plaques usually on the shins. Lupus pernio (LP) produces indurated 'bluish', nose, ear or cheek lesions in chronic sarcoidosis. Topical steroids may be effective in EN, but LP requires oral steroids, hydroxychloroquine or methotrexate therapy.
b.    Eye (e.g. uveitis and scleritis) involvement is more common in women and Afro-Caribbeans (>25%). Ophthalmology assessment is essential. Treatment is with oral steroids ( steroid eye drops).
c.   Cardiac disease (e.g. arrhythmias and heart failure) is uncom- mon ( 5%) in the USA and Europe but causes more than 70% of sarcoid-related deaths in Japan. Treatment is with high-dose steroids, antiarrhythmics and pacemakers.
d.   Neurosarcoid (5- 5% cases) causes nerve (e.g. mononeuritis multiplex) and focal cerebral (e.g. diabetes insipidus) lesions. Steroid and immunosuppressive therapy is often required.
Prognosis: factors associated with a relapsing course and poor out-come include age more than 40 years at onset, ethnic origin (e.g. Afro- Caribbean), extrathoracic disease and CXR stage (Fig. 3 e). Spontaneous remission usually occurs within 3 years and failure to remit within this time predicts a chronic course ( 0-30%) with death in 2-5% of cases. PFT have little prognostic value, but serial FVC and DLco detect progressive fibrosi which accounts for 87% of sarcoid-related deaths in the USA.