Genetics influence the clinical picture in sarcoidosis, a granulomatous heterogeneous disease often accompanied by elevated serum angiotensin converting enzyme (s-ACE). We aimed to investigate if certain HLA-DRB1 alleles correlate with the levels of s-ACE, known as a marker of the granuloma burden.

Medical journals of patients with sarcoidosis from a Swedish clinical registry were retrospectively examined to extract the highest recorded s-ACE value and analysed in relation to patient characteristics including phenotype [Löfgren syndrome (LS)/ non-LS], chest X-ray staging according to Scadding, treatment with immunosuppressants, presence of extrapulmonary manifestations (EPM), HLA-DRB1 alleles and prognosis (resolving vs. non-resolving disease within 2 years). Data were analysed with Fisher's exact test and Bonferroni correction was applied for HLA analyses.

Of 1204 patients included, 40% had s-ACE levels above reference value. In comparison with patients with normal s-ACE, those with elevated levels were more often classified into non-LS (78% vs 59%, p < 0.001), and Scadding stage II (50% vs 38%, p < 0.001) but less often Scadding stage I (33% vs 46%, p < 0.001) and had more often EPM (45% vs 23%, p < 0.001). The patients with HLA-DRB1×04 had more often elevated s-ACE (p < 0.01) while those with HLA-DRB1×03 commonly had normal levels (p < 0.001).

In this retrospective study, HLA alleles associated with s-ACE levels in sarcoidosis patients, which in turn correlated with occurrence of EPM. These findings shed some new light on possible mechanisms behind differences in s-ACE levels.