Childhood-onset systemic lupus erythematosus in Croatia: demographic, clinical and laboratory features, and factors influencing time to diagnosis

Objectives Childhood-onset systemic lupus erythematosus (cSLE) presents with diverse clinical features and often with non-classical symptoms that may delay diagnosis and increase risk of morbidity and mortality. This paper aims to analyse incidence, and clinical and laboratory features of cSLE in Croatia between 1991 and 2010, and to identify factors influencing time to diagnosis. Methods Medical records at three university-based tertiary care centres were analysed retrospectively for 81 children with cSLE (68 girls). Mean age at onset was 13.4 +/- 2.8 yr (interquartile range 3), and annual incidence varied from 1-15 per million at risk. Results The most frequent clinical and laboratory features were musculoskeletal symptoms (80%) and increased erythrocyte sedimentation rate (96%). The most frequent immunological laboratory findings were the presence of antibodies against histones (86%), double-stranded DNA (73%), and Sm protein (64%), as well as low levels of C3 complement (69%). Haematuria was present in 58% of children, proteinuria in 56%, and biopsy-confirmed lupus nephritis in 43%. Median time from symptom onset to diagnosis was 2 months (range 0-96). Time to diagnosis was inversely associated with ECLAM score (p<0.001), but it showed no association with age, gender, clinical features or distance from the nearest paediatric centre. Conclusion This is the first large-scale, in-depth study of clinical and laboratory features of cSLE in Croatia. Among all demographic, laboratory and clinical features examined, ECLAM score alone was inversely associated with time to diagnosis. This highlights the need to improve detection of children with fewer symptoms early in the course of the disease, therefore serious consequences for prognosis could be avoided.