HLA-alleles associated with increased risk for extra-pulmonary involvement in sarcoidosis

Genetic factors influence the risk for disease as well as the clinical picture seen in sarcoidosis and especially the genes localized to the human leukocyte antigen (HLA) region on chromosome 6 are of importance. The aim of this study was to further investigate associations between HLA-DRB1 alleles and the risk for extra-pulmonary manifestations (EPMs), i.e. engagement of the skin, superficial lymph nodes, eyes, nervous system, kidneys, hypercalcemia, parotid and salivary glands, heart, liver, spleen and bone marrow in Scandinavian sarcoidosis patients. One thousand patients with together with a group of 2000 healthy individuals, matched for sex and age. HLA-DRB1 alleles were determined for all patients and controls. Excluding erythema nodosum and ankle arthritis, we found 288 of 1000 patients to have EPMs. There were 383 patients with Löfgren's syndrome (LS), and among them EPM were relatively uncommon and diagnosed in only 31 (8.1%) of the patients. In contrast, among the 617 non-LS patients, 257 (41.6%) had EPM (P < 0.0001). In LS patients, the absence of HLA-DRB1*03 substantially increased the risk factor for EPM (erythema nodosum and ankle arthritis excluded) (P < 0.0001). A distinct HLA allele combination, HLA-DRB1*04/*15, was identified as a risk factor for EPM in all patients (25 of 50 with DRB1*04/15 had EPM). In conclusion, EPM are common in non-LS sarcoidosis. Furthermore, HLA-typing of sarcoidosis patients can be used in the clinic to identify patients with an increased risk for EPM.