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Sarcoidosis

Dr Ahmed Abd Rabou and Dr Frank Gaillard et al.

Sarcoidosis is a non-caseating granulomatous multi-system disease with a wide range of clinical and radiographic manifestations.

Common organ specific manifestations :

Epidemiology

Although the age of presentation is very broad, sarcoidosis most commonly affects patients between 20 and 40 years of age. There is a slight female predominance, particularly among African-Americans ^1,3. The overal incidence among Caucasians has been estimated at 20 per 100,000 ⁴.

Non caseating granuloma formation occurs in all affected tissues.

Clinical presentation

Clinical presentation is variable. Approximately 50% of patients are asymptomatic. The remainder present with either respiratory symptoms (e.g. cough and dyspnoea) or skin changes (e.g. erythema nodosum, lupus pernio, scars, plaques) ³. Although essentially any part of the body can be involved, ocular, lacrimal gland and salivary gland involvement are relatively common.

Approximately 5% of patients develop neurosarcoidosis ⁴.

A number of syndromes have been described:

Diagnosis is usually made on the combination of clinical and radiological features. Histology and / or a positive Kveim-Stilzbach skin test helps confirm the diagnosis ³.

Biochemical markers include:

elevated angiotensin-converting enzyme (ACE)
- 40% false negative
- 10% false positive ³
hypercalcaemia and hypercalciuria

Pathology

Sarcoidosis is a multi-system disorder of unknown aetiology characterized by the presence of widespread, non-caseating granulomas. It is thought to represent a disorder of immune regulation, particularly of cell mediated immunity ³. Mycobacterium and Propionibacterium RNA and DNA has been detected in sarcoidosis lesions raising the possibility of an infective component ⁴.

Characteristic (but not pathognomonic) histological features include:

non-caseating epithelioid granulomas
Schaumann bodies : laminated Ca₂₊ containing concretions
asteroid bodies

The granulomas may resolve spontaneously or progress to fibrosis.

Radiographic features

As 90% of patients have pulmonary involvement, and chest x-rays are readily available and have low radiation burden, the pattern of nodal and parenchymal involvement is used to 'stage' sarcoidosis : see chest x-ray staging of sarcoidosis ³.

Please refer to organ specific articles:

Radiographic signs:

chest x-ray
- 1-2-3 sign or Garland triad
CT
- sarcoid galaxy sign ²
Gallium⁶⁷scintigraphy
- panda sign
- lambda sign

Treatment and prognosis

Treatment is primarily with corticosteroids, which must however be used judiciously.

Pulmonary involvement is responsible for the majority of morbidity and mortality in patients with sarcoidosis. The overall mortality rate is approximately 5%, with patients who present insidiously faring worse than those who present with an acute onset ^1,3. Likelihood of resolution depends stage of disease at presentation ³:

stage I : 60% resolution within 1-2 years
stage II : 46%
stage III : 12%

Complications

Complications are of course organ dependent. As pulmonary sarcoidosis is by far the most common manifestation, so are thoracic complications. They include ³: