Phenotyping of Sarcoidosis: Moving (a step closer) Towards Sarcoidosis as a Syndrome

Sarcoidosis is a granulomatous disease of unknown origin affecting mostly the lungs. Lung involvement exhibits different radiological patterns in HRCT and ventilatory defects in lung function raising the question, whether sarcoidosis is an umbrella term, which embraces different disease phenotypes. We investigated the radiological and lung functional phenotypes in a cohort of 261 patients with sarcoidosis. CT scans were assessed by two experienced radiologists based on a semi-quantitative scoring system and corresponding lung functions were categorized as restrictive (TLC < 80% of predicted and FeV1/FVC≥0.7), obstructive (TLC ≥80%pred and FeV1/FVC < 0.7), mixed (TLC < 80% of predicted and FeV1/FVC < 0.7) or diffusion impairment only (TLC ≥80%pred and FeV1/FVC≥0.7 and DLCO<80% of predicted) or otherwise “normal”. 261 patients with 250 available CT scans were included (56% female) with a mean age of 49.4 years (± 14.9). 30% patients exhibit normal lung function, 22% of patients had a restrictive, 11% an obstructive, 15% a mixed ventilatory defect and 22% of patients had a diffusion impairment only. Nodules (either bronchocentric or perilymphatic) were the most common findings in 107 (42.8%) patients and normal CT was present in 49 (19.6%) patients. Extrapulmonary sarcoidosis manifestations were present in 44.4% of patients, notably with lower prevalence in patients with bronchocentric consolidations or architectural distortion. In these patients obstructive or mixed ventilatory defects represents the majority of lung function findings in 67% and 83% of patients, respectively. In summary, different radiological phenotypes seem to correlate with different clinical and lung functional presentation.