Sarcoidosis

Notes

Definition & classification

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.

Pulmonary sarcoidosis

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:

  • Fine inspiratory crackles
  • Exertional desaturations
  • Clubbing 

Additionally pulmonary disease may lead to a number of complications:

  • Pulmonary artery hypertension
  • Cor pulmonale

Ocular sarcoidosis

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

Uveitis is the Inflammation of the uvea, a structure composed of (from anterior to posterior) the iris, ciliary body and choroid.

  • Anterior uveitis is the inflammation of the iris (iritis) and may involve part of the ciliary body (cyclitis). Pain, redness and photophobia are typical.
  • Intermediate uveitis is the inflammation of parts of the ciliary body.
  • Posterior uveitis is the inflammation of the choroid (choroiditis). It may involve retinal vasculitis. Symptoms include floaters and visual loss.

Panuveitis describes inflammation of the entire uveal structure.

Other ocular pathologies

  • Keratoconjunctivitis sicca (dry eye syndrome)
  • Adnexal granulomas
  • Secondary glaucoma

Cutaneous sarcoidosis

Skin manifestiations are seen in around 25% of patients with sarcoidosis

A number of rashes may be seen:

  • Papular sarcoidosis: multiple papules develop, generally on the head and neck or areas of trauma.
  • Erythema nodosum: a panniculitis (a condition with inflammation of subcutaneous adipose tissue) characterised by red, painful nodules. 
  • Lupus pernio: a violaceous, nodular rash distributed over the nose and cheeks. It is pathognomonic but rare.

Other manifestations

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.

Spirometry

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. 

  • FVC: the forced (expiratory) vital capacity is a persons maximal expiration following full inspiration.
  • FEV1: the forced expiratory volume in one second, i.e the volume of FVC expelled after one second.

Restrictive pattern

The following changes are seen in restrictive lung disease such as sarcoidosis:

  • FVC: reduced.
  • FEV1: reduced.
  • FEV1/FVC: > 80%.

Investigations & Diagnosis

Bilateral hilar lymphadenopathy is a characteristic finding in sarcoidosis. 

Bedside

  • Observations
  • Mantoux test - to rule out TB, another granulomatous disease that may cause erythema nodosum.

Bloods

  • Full blood count (FBC)
  • Urea & electrolytes (U&Es)
  • ESR/PV
  • Bone profile:
    • Hypercalcaemia is seen in around 15%.
  • Serum ACE:
    • Raised in around 70%, levels show a response to treatment. However, it is not accurate enough to be used diagnostically and has limited prognostic value. 

Imaging

A chest x-ray may reveal bilateral hilar lymphadenopathy and reticular opacities.

Depending on disease progression high-resolution CT may demonstrate:

  • Lymphadenopathy
  • Diffuse nodularity
  • Ground glass opacification
  • Fibrosis typically affecting the upper lobes

Special

Brochoalveolar lavage ± transbronchial biopsy:

  • Inversion of CD4/CD8 ratio
  • Raised lymphocytes
  • Biopsy demonstrating non-caseating granuloma

Staging

Pulmonary sarcoidosis may be staged based upon chest radiograph findings.

Sarcoidosis staging

Management

Mild disease may not require treatment, steroids are used in advanced and symptomatic disease.

Pulmonary sarcoidosis

  • Sarcoidosis requires specialist management
  • Algorithm is based on BTS Interstitial lung disease guideline (August 2008).

  • The dose of prednisolone is typically between 20-40mg a day.
  • Steroids are generally continued for 4-6 weeks. At this time, CXR and lung function tests may be repeated. If improvement is seen the dose may be tapered, if not they are continued with reassessment. 

Extrapulmonary sarcoidosis

  • Eye involvement, hypercalcaemia and other extrapulmonary involvement are indications for steroids.
  • Severe or persistent erythema nodosum is an indication for a short course of steroids.

Prognosis

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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