Pulmonary Sarcoidosis: A Narrative Review of the Uneven Epidemiologic Landscape in Europe and Diagnostic Complexity

Abstract:

Pulmonary sarcoidosis is the most frequent presentation of sarcoidosis and remains difficult to define epidemiologically and diagnostically. This review summarizes contemporary evidence on the uneven epidemiologic landscape of pulmonary sarcoidosis in Europe and discusses current diagnostic approaches with emphasis on persistent limitations. Available European data show marked heterogeneity, with the strongest estimates derived from national registry- or populationbased studies in Northern Europe and England. In contrast, other available data remain regional, administrative, historical, or fragmented. Diagnostically, sarcoidosis remains a clinical-radiologicalhistological diagnosis rather than a single-test-confirmed disease. A compatible presentation, nonnecrotizing granulomatous inflammation, and exclusion of alternative disorders remain central, but each component has limitations. Chest radiography and high-resolution computed tomography are essential for detecting intrathoracic lymphadenopathy, parenchymal patterns, and fibrotic transformation; however, imaging is not fully specific. Serum biomarkers and bronchoalveolar lavage may support suspicion but cannot independently confirm the diagnosis. Histological confirmation increases diagnostic certainty, although it may be omitted in selected highly typical scenarios. The main unresolved problems are the lack of a specific biomarker, the incomplete standardization of exclusion algorithms, the limitations of current staging systems, and the variability in biopsy decisions.