Sarcoidosis and Other Immune-Related Conditions
Michael J. Thrall, MD
Key Facts
Clinical Issues
Sarcoidosis is a granulomatous disease most often involving lung and mediastinum
Rheumatoid nodules may form in the lung or pleura
Eosinophilic pneumonia is diagnosed by the presence of markedly increased eosinophils
Cytopathology
Multinucleated giant cells and epithelioid histiocyte aggregates are typical of sarcoidosis
Rheumatoid nodules may shed concerning epithelioid histiocytes with bizarre morphology
Ancillary Tests
Fungal and mycobacterial stains to rule out organisms are essential in granulomatous diseases
Top Differential Diagnoses
Granulomatous inflammation due to infectious etiologies
Other granulomatous responses
 (A) Aggregates of epithelioid histiocytes, seen here on a Diff-Quik stain, help to identify granulomatous inflammation. The lack of necrosis is compatible with the diagnosis of sarcoidosis. (B) The possibility of sarcoidosis may only be suggested by occasional giant cells, seen here in a Pap-stained bronchial brushing. (C) Inclusions within giant cells, such as the asteroid body  seen on this Pap stain, are common in sarcoidosis but not specific. These should not be confused with an organism or foreign material. (D) An H&E-stained histology section demonstrates the small, nonnecrotizing granulomas typical of sarcoidosis. |
CLINICAL ISSUES
Sarcoidosis
Granulomatous disease most often involving lung and mediastinum
Etiology is unknown
Diagnosis of exclusion requiring elimination of known infectious and other causes of granuloma formation
Elevated angiotensin-converting enzyme (ACE) levels in serum may aid diagnosis
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