Childhood-onset of primary Sjögren's syndrome: phenotypic characterization at diagnosis of 158 children.

Objectives To characterize the phenotypic presentation at diagnosis of childhood-onset primary Sjogren syndrome (SjS). Methods The Big Data Sjogren Project Consortium is an international, multicentre registry using worldwide data-sharing cooperative merging of pre-existing clinical SjS databases from the five continents. For this study, we selected those patients in whom the disease was diagnosed below the age of 19 according to the fulfilment of the 2002/2016 classification criteria. Results Among the 12 083 patients included in the Sjogren Big Data Registry, 158 (1.3%) patients had a childhood-onset diagnosis (136 girls, mean age of 14.2 years): 126 (80%) reported dry mouth, 111 (70%) dry eyes, 52 (33%) parotid enlargement, 118/122 (97%) positive minor salivary gland biopsy and 60/64 (94%) abnormal salivary ultrasound study, 140/155 (90%) positive antinuclear antibody, 138/156 (89%) anti-Ro/La antibodies and 86/142 (68%) positive rheumatoid factor. The systemic ESSDAI domains containing the highest frequencies of active patients included the glandular (47%), articular (26%) and lymphadenopathy (25%) domains. Patients with childhood-onset primary SjS showed the highest mean ESSDAI score and the highest frequencies of systemic disease in 5 (constitutional, lymphadenopathy, glandular, cutaneous and haematological) of the 12 ESSDAI domains, and the lowest frequencies in 4 (articular, pulmonary, peripheral nerve and central nervous system) in comparison with patients with adult-onset disease. Conclusions Childhood-onset primary SjS involves around 1% of patients with primary SjS, with a clinical phenotype dominated by sicca features, parotid enlargement and systemic disease. Age at diagnosis plays a key role on modulating the phenotypic expression of the disease.