Sarcoidosis is a rare multisystem granulomatous disorder of unknown aetiology.
It is thought to have a prevalence of around 1-2 per 10,000 though it more commonly affects blacks who also tend to suffer from more severe disease. The condition typically affects those aged between 20 and 50.
The aetiology, though poorly understood, is thought to involve immune dysfunction and T-cell overactivity. It most frequently affects the lungs causing a form of interstitial lung disease.
The condition features noncaseating granulomas, which may be defined as a collection of epithelioid histiocytes that develops in response to a persistent stimulus.
The lungs are affected in 90% of patients, though signs and symptoms may be absent or subtle.
Sarcoidosis causes an overactive cellular immune response. Advanced pulmonary sarcoidosis involves the development of fibrosis causing thickening of the pulmonary interstitium. Bilateral hilar lymphadenopathy is the hallmark finding on chest radiograph.
The main symptom (if indeed symptoms are present) is progressive breathlessness.
If fibrosis develops a number of signs may be identified on examination:
Additionally pulmonary disease may lead to a number of complications:
The eyes are affected in around 30-60% of cases most commonly in the form of uveitis.
Sarcoidosis may lead to a number of ocular pathologies.
Uveitis is the Inflammation of the uvea, a structure composed of (from anterior to posterior) the iris, ciliary body and choroid.
Panuveitis describes inflammation of the entire uveal structure.
Skin manifestiations are seen in around 25% of patients with sarcoidosis
A number of rashes may be seen:
Hypercalcaemia is seen in around 15% of cases. This occurs due extra-renal synthesis of calcitriol causing 1-α hydroxylation of 25-hydroxyvitamin D and so increased levels activated vitamin D. This leads to increased levels of calcium.
Renal disease may occur but is rarely clinically relevant. Significant renal disease sometimes occurs secondary to hypercalcaemia which may cause nephrocalcinosis. Granuloma formation can lead to interstitial nephritis but this is rarely of significance.
CNS disease is rare but may be severe. Arthralgia and bone cysts (particularly in the digits) and hepatosplenomegaly may be seen. Cardiac involvement is rare, it can present with arrhythmias, cardiomyopathy and heart failure.
Heerfordt's syndrome, also termed uveoparotid fever, is a variant of sarcoidosis characterised by uveitis, parotid swelling, fever and facial nerve palsy.
Löfgren's syndrome is an acute variant of sarcoidosis characterised by bilateral hilar lymphadenopathy, erythema nodosum, arthralgia and fever.
In cases of pulmonary sarcoidosis with pulmonary infiltrates and fibrosis a restrictive lung disease pattern is seen.
Spirometry measures the flow and volume of air during inhalation and exhalation.
The following changes are seen in restrictive lung disease such as sarcoidosis:
Bilateral hilar lymphadenopathy is a characteristic finding in sarcoidosis.
A chest x-ray may reveal bilateral hilar lymphadenopathy and reticular opacities.
Depending on disease progression high-resolution CT may demonstrate:
Brochoalveolar lavage ± transbronchial biopsy:
Pulmonary sarcoidosis may be staged based upon chest radiograph findings.
Mild disease may not require treatment, steroids are used in advanced and symptomatic disease.
In untreated indivduals the overall mortality rate for sarcoidosis is normally quoted at 5%.
The majority of patients with early stage disease will acheive remission with a significant number not requiring medical intervention.
The disease is known to be more severe in certain races, in black Americans mortality rates of 10% have been seen. Progressive fibrosis, pulmonary artery hypertension and cor pulmonale are the most frequent causes of death. Less commonly myocardial disease may result in death.
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