In sarcoidosis, any organ may be affected, and the majority of cases have pulmonary involvement. The disease course in pulmonary sarcoidosis varies considerably, from complete resolution to chronic disease and/or pulmonary fibrosis. The heterogeneity of sarcoidosis is a major challenge in treatment decision-making, and the hope is that subgrouping patients into phenotypes may help to provide the right care for the right patient. In this issue of Thorax, Sharp et al 1 provide evidence that sarcoidosis phenotypes, based on pulmonary function tests (PFTs), predict lung function decline over time. They found that individuals with a restrictive pulmonary phenotype had a greater 3-year loss in pulmonary function compared with those without impairment. Furthermore, black individuals had a less favourable course compared with white individuals who improved in pulmonary function over time.

The study by Sharp et al included longitudinal data with several years of follow-up, which is an improvement over previous studies which were based on cross-sectional data. Prognosis prediction in sarcoidosis is challenging due to the wide variation across patients, and many studies have not been replicated. Previous studies have examined different blood-based biomarkers, but it is still unclear whether these are reliable and useful to predict progression to fibrosis. Some more recent …