Sarcoidosis

CLINICAL HISTORY

A 52-year-old woman with a history of asthma presented to the emergency department with chest pain and shortness of breath. The patient had no smoking history and the rest of her medical history was unremarkable.

FINDINGS

A CT scan of the chest using a pulmonary angiography protocol was obtained to evaluate for pulmonary embolism. CT axial lung (Figure 1) and soft tissue (Figure 2) images demonstrate multiple peripheral pulmonary nodules. Of note are the smooth borders of the nodules without calcifications and the air bronchograms within the nodules in the right middle lobe. A coronal CT image (Figure 3) also demonstrates multiple smooth-bordered peripheral nodules, some containing air bronchograms. Figure 4 demonstrates right hilar adenopathy. Left hilar adenopathy was also observed (figure not shown).

DIAGNOSIS

Sarcoidosis

DIFFERENTIAL DIAGNOSIS

Metastatic disease, lymphoma, septic emboli, rheumatoid nodules, Wegener's granulomatosis, varicella infection, atypical infections (mycobacterium avium complex, cytomegalovirus, cryptococcus).

DISCUSSION

Sarcoidosis is a multisystem disorder of unknown etiology characterized by the presence of noncaseating granulomas. Although sarcoidosis may involve almost any organ system, pulmonary disease causes the most morbidity and mortality. In more than 90% of cases, the pulmonary parenchyma/pleura and intrathoracic lymph nodes are involved. About 25% of patients will have respiratory symptoms as their presenting complaint.

Plain radiographic findings have been described as occurring in specific stages:

Stage 0: No visible abnormalities;

Stage 1: Hilar or mediastinal lymph node enlargement not associated with lung disease (half of all patients present with stage 1 disease);

Stage 2: Hilar or mediastinal lymph node enlargement associated with lung disease;

Stage 3: Diffuse lung disease without lymph node enlargement;

Stage 4: End-stage fibrosis.

Lymphadenopathy is present in over 80% of cases of sarcoidosis. Typically, nodal enlargement involves the hilar and mediastinal lymph nodes and is usually bilaterally symmetric. Less likely, enlarged lymph nodes can be found in the subcarinal space and anterior mediastinum. Unlike adenopathy caused by neoplastic disorders, nodes in sarcoid tend to maintain their shapes and borders as they enlarge, rather than tending to coalesce. Lymph nodes may become quite large. Half contain calcifications discernible on CT.

Four patterns of parenchymal disease are demonstrated on CT in patients with sarcoidosis: linear interstitial infiltrates, multinodular disease, mixed pattern, and mass-like consolidation.

In multinodular disease, the size and distribution of nodules varies. The nodules may be small (1 to 3 mm), and evenly distributed throughout the lung fields in a miliary pattern, or they may be more unevenly scattered and larger in size (4 to 6 mm).

When sarcoid nodules become larger and more numerous, they begin to coalesce and to encroach upon the surrounding alveolar spaces. These patients will demonstrate round, mass-like consolidations, as demonstrated in the illustrated case. This form of sarcoid is often referred to as “alveolar” or “acinar” sarcoid. Masses often resemble metastatic disease and may have air bronchograms. They represent the coalescence of numerous granulomas within the interstitium forming massive conglomerates that compress the surrounding airspace, and do not cause actual airspace filling.

Submitted by Andrew Allmendinger D.O., and Robert Perone M.D., both with St. Vincent's Medical Center, New York, NY.

BIBLIOGRAPHY

Nishimura K, Itoh H, Kitaichi M, et al. Pulmonary sarcoidosis: correlation of CT and histopathologic findings. Radiology 1993;89(1):105-109.

Kuhlman JE, Fishman EK, Hamper UM, Siegelman SS. The computed tomographic spectrum of thoracic sarcoidosis. Radiographics 1989;9(3):449-466.

Koyama T, Ueda H, Togashi K, et al. Radiologic manifestations of sarcoidosis in various organs. Radiographics 2004;24(1):87-104.

Webb WR, Higgins CR. Thoracic imaging: pulmonary and cardiovascular radiology. Philadelphia: Lippincott Williams & Wilkins, 2005:339-448.