Sarcoidosis (thoracic manifestations)

Pulmonary and mediastinal involvement of sarcoidosis is extremely common and is seen in over 90% of patients. Radiographic features are variable depending on the stage of the disease. 

For a general discussion, please refer to the parent article: sarcoidosis.

Pulmonary manifestations are present in ~ 90% of patients. Pulmonary sarcoidosis most commonly affects patients between 20 and 40 years of age although it is seen essentially at any age 1. There is a slight female predominance, particularly among African-Americans and it is rare in Asians.

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.

Löfgren syndrome is an uncommon but specific acute presentation with a better prognosis.

Respiratory function tests tend to demonstrate a restrictive pattern with reduced lung volumes and reduced diffusion capacity. Obstructive components are usually seen in patients who also smoke, and are primarily attributable to the later 6.

Grossly multiple granulomas are seen in a characteristic lymphatic and perilymphatic distribution. Microscopically the granulomas are typically non-caseating and coalescent. Sarcoid granulomata are distributed mainly along the lymphatics in the bronchovascular sheath and, to a lesser extent, in the interlobular septa and subpleural lung regions. This distribution is one of the most helpful features in recognising sarcoidosis pathologically and is responsible for the high rate of success in diagnosis by bronchial and transbronchial biopsies 10.

The granulomas may resolve spontaneously or progress to fibrosis.

Both chest radiograph and CT are commonly used to evaluate for pulmonary sarcoidosis. Imaging evaluation can be tricky, as the manifestations are variable and depend on the stage of disease on both x-ray and CT.

Although there is a large spectrum of often non-specific thoracic imaging findings (sarcoidosis is often termed the "great mimicker" 7), the most typical manifestations include:

  • symmetric mediastinal lymphadenopathy
  • pulmonary parenchymal changes, ranging from perilymphatic micronodules to pulmonary fibrosis (end-stage disease)

It is essential to understand that imaging findings are non-specific or atypical in 25-30%, and chest radiograph is normal despite the presence of pulmonary granulomas histologically 5-10%.

Given the clinical significance of pulmonary manifestations in sarcoidosis, imaging is used to help stage disease:

The most common manifestation is bilateral hilar and mediastinal nodal enlargement, which is seen at some stage during the illness in over three-quarters of patients 1,3:

  • 1-2-3 sign or Garland triad is the classic finding, representing bilateral hilar and right paratracheal nodal enlargement 3
    • involvement of right paratracheal nodes is not 'magical' but reflects the sensitivity of x-ray for detecting abnormality at this nodal station
    • left paratracheal and aortopulmonary nodes are also frequently enlarged, but harder to identify
  • nodal distribution
    • if there is lymphadenopathy, hilar nodes are almost always involved
    • rare to have middle mediastinal nodal involvement without the hilar involvement
    • unilateral hilar enlargement without mediastinal involvement is rare, seen only in 1-3% of cases 3
    • anterior and posterior nodal enlargement is uncommon, and almost always seen in combination with mediastinal and hilar involvement 3
    • atypical patterns of nodal enlargement are more frequently seen in patients ≥50 years of age at presentation 3
  • nodes can be very large but typically do not abut the cardiac silhouette, in contrast to lymphoma in which the nodes are continuous with the pericardial outline 1
  • eventual calcification of intrathoracic nodes is seen in 20% of cases after ten years
    • pattern of calcification is variable and includes: punctate; amorphous, or eggshell (5%) 1,3

Parenchymal features vary depending on the individual patient and the stage of the disease. They include 1-3:

Although chest x-ray may be sufficient for the diagnosis of sarcoidosis, CT or high-resolution CT provides more sensitive and specific evaluation for lung changes and lymphadenopathy, as well as corollary findings such as pulmonary artery enlargement or sequela of cystic disease (e.g. mycetoma formation). Consequently, CT allows a more accurate correlation to disease stage and also to pulmonary function tests 17. It may be especially useful in patients with normal (stage 0) or isolated nodal involvement (stage I) by chest x-ray 3.

Parenchymal findings include 1-5:

  • irregular nodular thickening in a perilymphatic upper/mid lung distribution
  • small nodules may dominate and appear similar to miliary opacities 15
  • nodules or large opacities measuring 1 to 4 cm
    • confluence of many smaller nodules, thus irregular margins
    • seen in 15 to 25% of patients
    • may mimic consolidation
    • frequently contain air bronchograms
  • ground-glass opacities
    • represent extensive interstitial sarcoid granulomas below the resolution of HRCT rather than alveolitis
  • features of small airways disease
  • pulmonary fibrosis - represents stage IV disease
    • three main patterns described corresponding to pulmonary function testing results 17,18:
      1. central bronchial distortion or bronchiectasis featuring air trapping, with predominantly obstructive physiology
      2. peripheral honeycombing, with predominantly restrictive physiology and low DLCO:
        • usually a minor feature and present only in severe fibrosis
        • subpleural
        • mainly the middle and upper lung zones
        • lower lobes predominance resembling UIP is rare
      3. diffuse linear fibrotic pattern, with more mild effect on respiratory function
        • typically radiate away from hila in all directions
    • the pattern of distortion of lung architecture may be mixed:
      • posterior displacement of the upper lobe bronchi, indicating loss of volume in the posterior segments of the upper lobes
      • upward and outward retraction of hila
      • compensatory hyperinflation of the lower lobes
      • traction bronchiectasis
  • pulmonary cysts
  • air trapping on expiratory phase 6
    • patchy air trapping at the level of the secondary lobules
    • air trapping is presumably secondary to bronchiolar obstruction by submucosal granulomas
    • much more pronounced in patients who are also smokers

Characteristic hilar/mediastinal lymphadenopathy is better seen on CT:

  • present in 80-90% of patients
  • distribution tends to be symmetrical, with hilar and middle mediastinal involvement.
  • calcification of hilar and mediastinal lymph nodes relatively common

Pleural involvement is infrequent 17:

  • pleural effusion (bland, chylous, hemorrhagic)
  • pleural thickening/plaques

Tracheal or bronchial involvement is only rarely seen but may result in stenosis 3.

Sarcoidosis is characteristically FDG-avid, and PET/CT has been shown to have high sensitivity (94-100%) for thoracic disease 17.  Thus, FDG-PET/CT may be useful for 12,17:

  • identification of occult sites of disease
  • identifying a suitable target for diagnostic biopsy
  • gauging active inflammatory disease in patients with prolonged symptoms
  • assessing response to treatment

Gallium-67 scintigraphy usually shows high uptake in active sarcoidosis and is useful for assessing disease activity and response to treatment, although as it is a non-specific marker of inflammation, it is non-specific. It has a role also in detecting extra-thoracic involvement (see sarcoidosis) 3.

The gallium equivalent of 1-2-3 sign or Garland triad is known as the lambda sign.

Treatment is predominantly with corticosteroids, which are usually administered only to patients with active disease. Unfortunately distinguishing active disease superimposed on chronic fibrotic changes is difficult and criteria are controversial 5.

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 on the stage of disease at presentation 3:

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

Recognised complications include 3:

The differential often depends on the stage of disease and particular appearances:

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Article information

rID: 5146
System: Chest
Synonyms or Alternate Spellings:
  • Pulmonary sarcoidosis
  • Sarcoidosis (lung manifestations)
  • Sarcoidosis (pulmonary and mediastinal manifestations)
  • Sarcoidosis (mediastinal manifestations)
  • Thoracic sarcoidosis
  • Pulmonary and mediastinal manifestations sarcoidosis
  • Pulmonary manifestations of sarcoidosis
  • Sarcoidosis (pulmonary manifestations)
  • Sarcoidosis (chest)

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