Erythema nodosum in sarcoidosis. Relationship with extrathoracic involvement and prognostic significance.

Introduction: Only a few studies analysed the prognosis significance of erythema nodosum (EN) in sarcoidosis. Our objective was to analyze the prevalence of EN in sarcoidosis, its possible association of EN with extrathoracic sarcoidosis, and its prognostic significance.

Methods: Retrospective study including patients diagnosed with sarcoidosis at Bellvitge University Hospital, Barcelona, Spain, between 1980 and 2017. Patients were followed up prospectively at the sarcoid clinic of the hospital. Patients' medical records were reviewed to obtain the clinical data.

Results: 728 patients (494 women and 234 men, mean age 43.45 years SD 13,833) were diagnosed with sarcoidosis. Radiological stages were 0 in 68 patients (9.34%), 1 in 434 (59.62%), 2 in 167 (22.94%), 3 in 45 (6.18%) and 4 in 14 (1.92%). Pulmonary fibrosis at 5 years of follow up was documented in 44 patients. EN was diagnosed in 269 (37%). In 265 cases (98.5%), EN lesions were present at the onset of sarcoidosis and mostly corresponded to radiological stage 1 at diagnosis (82.52%). Among patients with EN, 3/269 had pulmonary fibrosis at 5 years of follow-up (p<0.001), sarcoidosis activity persist for more than 5 years in 28/269 (p<0.001), and oral corticosteroids were required in 48/269 patients (p<0.001). Patients with EN had a low incidence of severe extrapulmonary involvement.

Conclusion: EN was observed in 37% of sarcoidosis patients, usually at the onset of the disease. Patients with EN-associated sarcoidosis have mainly radiological stages 1 at diagnosis, and are at lower risk of chronicity, pulmonary fibrosis, and severe forms of extrathoracic organ involvement.