Laboratory Investigations and Immunological Testing in Sarcoidosis

Abstract

Sarcoidosis is a systemic granulomatous disease of unknown aetiology, which can affect virtually any organ and is thus characterised by a variable clinical presentation and course. The disease is generally considered to be a T helper-1 (TH1) type of reaction, although TH2 and TH17 features have also been identified. Approximately 90% of patients demonstrate disease involvement of the lungs and thoracic lymph nodes and although sarcoidosis is usually subacute and self-limiting, progressive inflammation can lead to pulmonary fibrosis and death. Despite these features, there is currently no definitive single laboratory investigation used to identify sarcoidosis, indicating the need for improved understanding of the immuno‐ pathogenesis and identification of disease-specific biomarkers. Currently, sarcoidosis is generally a diagnosis of exclusion that is best confirmed by clinical and radiological findings and tissue biopsies revealing non-caseating granulomas in the absence of known granuloma‐ genic agents. Laboratory testing is nonetheless beneficial in further supporting a diagnosis of sarcoidosis and assessing disease severity.