Clinical History
A 45-year-old man was admitted to the hospital with one-year history of dry, non-resolving cough and fever. Chest radiograph (Fig. 1) was performed followed by thoracic CT scan (Fig. 2) and EBUS (Endobronchial Ultrasound) biopsy. Histopathology was positive for non-necrotic epithelial granulomas.
Imaging Findings
Chest radiograph (Fig. 1) revealed diffused, multiple small nodular opacities predominantly located in the upper lung lobes. There was a moderate bilateral hilar lymphadenopathy.
CT scan (Fig. 2) showed bilateral hilar, lymph node enlargement. There were numerous well-defined small nodules predominantly seen in a perilymphatic distribution in the upper and middle lung zones. Locally they tended to coalesce together forming consolidations, primarily in both upper and middle lung zones.
Discussion
Sarcoidosis is a granulomatous multisystem disease of unknown aetiology. Even though non-necrotising granulomas characteristic for this disease may be present in any organ, thoracic involvement is most common and is responsible for most of morbidity and mortality. [1]
Sarcoidosis can manifest in highly characteristic manner as a Lofgren’s or Heerfordt’s syndrome; however, in most cases initial symptoms are non-specific or even absent at all. Incidental abnormal chest radiograph is not an uncommon first finding. [2]
Most common chest radiograph findings include hilar and mediastinal lymphadenopathy followed by interstitial lung disease. Pattern of chest radiological abnormalities is a basis for classic sarcoidosis classification. (Fig. 3) [3]
Stage 2, observed in 25-30% of first time presenting patients, is described as a hilar and mediastinal lymph node enlargement associated with pulmonary abnormalities. Lymphadenopathy pattern is similar to that of stage 1 disease (Fig. 4), where 85-90% patients have symmetric, bilateral, well-defined, enlarged hilar lymph nodes. In 75% of cases mediastinal lyphadenopathy is also present. [4]
Small nodules are the most common parenchymal changes, present in approximately 75-90% of patients. Although these lesions are predominantly found in the upper and middle lung zones, they can also occur in the lower lung zones. Nodules are primarily seen in peribronchovascular and supleural localisation, less frequently in the interlobular septa. In rare cases of patients with extensive disease, micronodules can appear to be randomly distributed. Even though they are initially individual lesions, they can coalesce over time forming larger entities. Such changes, observed in 15-25% of patients, take appearance of irregular consolidation measuring 1-4 cm. They can have airbronchogram and in solitary cases cavitate - which should raise question of fungal or mycobacterial infection. On periphery of consolidation individual small nodules can be spotted - an image named “galaxy sign”. Even though these consolidations are commonly called “alveolar sarcoidosis”, in fact they are the result of numerous interstitial micronodules coalescing together. [5]
Airway abnormalities are relatively common in sarcoidosis, observed in 65% of patients. Most common manifestation is bronchial wall thickening and small endobronchial lesions. Hardly ever they lead to lobar or segmental atelectasis. [4]
Pleural involvement is uncommon, it can present as a pleural thickening or pleural effusion. Effusions are typically minimal and usually resolve spontaneously in 2-3 months. However, there have been singular reports of massive pleural effusions. [5]
Take home message
Small nodules in perilymphatic distribution in association with symmetric bilateral hilar lymphadenopathy is a classic appearance of stage 2 sarcoidosis.
Alveolar sarcoidosis is a term describing coalescing interstitial small nodules.
Differential Diagnosis List
Stage 2 sarcoidosis
Infectious:
Tuberculosis
Mycoplasmosis
Histoplasmosis
Blastomycosis
Coccidiomycosis
Cat scratch disease
Malignancy:
Lymphangiosis carcinomatosa
Lymphoma
Cancer
Inorganic dust diseases:
Berylosis
Silicosis
Other:
Hypersensivity pneumonitis
Drug reactions
Amyloidosis
