Background SLE is a rare chronic autoimmune disease with polymorphic clinical manifestation and wide-ranging disease course with treatment tactics dependent on disease activity and organ involvement. In 2017, a study to estimate prevalence and incidence of SLE in Estonia was done, but there is no data published to describe the Estonian SLE population. The aim of the present study is to analyze a sample of Estonian SLE patients.

Methods Consecutive outpatient and inpatient patients with rheumatologist diagnosed SLE (≥20 years) were enrolled in East-Tallinn Central Hospital. Two study visits were done with 6 months apart to evaluate disease activity, current treatment, organ involvement, immunological findings and comorbidities. In addition, data from medical records were collected: organ involvement and immunological findings at the time of diagnosis and initial treatment. SLE disease activity was measured using SLEDAI 2K (Systemic Lupus Erythematosus Disease Activity Index 2K) score.

Results Among 40 patients (mean age 50 (standard deviation ±12.4) years, mean disease duration 12 (±9.9) years, mean SLEDAI 2K at diagnosis 10 (±3.9)) 92.5% were females. Mean SLEDAI 2K value at entering into the study was 4 (±3.4) similar to the value after six months 4 (±4.9). 82.5% of patients received hydroxychloroquine and 75% glycocorticosteroid treatment, 27.5% of patients were treated with rituximab. During their disease course 90% had joint and 50% skin involvement, 35% had leucopenia, all patients were positive for antinuclear antibody (ANA), 80% were anti-double-stranded DNA antibody (anti-dsDNA) positive and 70% of patients had low complement levels.

Conclusion The first analysis of Estonian SLE patients’ clinical and laboratory parameters indicates that the disease is overall well managed in most of the patients. Further studies are in progress on collected serum and PBMC samples to find immunological causes for poor treatment response.