Hip involvement in children with enthesitis related arthritis (ERA) is associated with poor outcomes in adulthood

BACKGROUND: The data on long-term outcome in enthesitis-related arthritis (ERA), the commonest category of JIA in India, is scant. Thus, we studied outcomes of ERA in a resource-constrained setting. METHODS: Patients with ERA (ILAR classification) (≥ 5 years of disease and ≥ 18 years) were included. Data on clinical features, Bath indices (BASMI, BASDAI, BASFI), ASDAS, and health assessment questionnaire-disability index (HAQ-DI) was collected. X-ray pelvis including hips was obtained and compared with baseline X-ray for progression of sacroiliitis and hip arthritis. Fulfillment of adult criteria of spondyloarthropathy (SpA) were also assessed. RESULTS: Seventy-three 73 patients (72 males) of median age 20 (18–23) years and disease duration 8 (5.5–11) years were recruited. There was delay in diagnosis of 4 (1.75–6) years. Thirty-nine (53%) had BASDAI ≥ 4 and 63 (91%) had ASDAS-CRP > 1.3. Two-third (60%) had functional disability (HAQ-DI ≥ 0.5). Poor outcome (BASDAI ≥ 4, ASDAS > 2.1, BASFI > 0.9, or HAQ-DI ≥ 0.5) was seen in three-fourths (n = 56.76%) of patients and was associated with hip involvement, HLA-B27 positivity, and fulfillment of axial ASAS criteria. Sixty-seven (91%) patients fulfilled axial ASAS criteria, while 71 (97%) fulfilled peripheral ASAS criteria. Overall, 81% had X-ray sacroiliitis and 37% had hip involvement. Nearly half (46.6%) and one-fourths (25%) of the patients had X-ray sacroiliitis and hip arthritis progression, respectively. Those with X-ray hip arthritis had longer delay in diagnosis (6 vs 3 years), higher Bath indices, ASDAS, and HAQ-DI. Hip arthritis correlated with radiological sacroiliitis (r = 0.301). Fulfillment of modified NY criteria was seen more often in patients with hip arthritis (95 vs 63%; p < 0.002). CONCLUSION: Most ERA patients had active disease in adulthood. Hip involvement, axial involvement, and HLA-B27 positivity were predictors of poor outcome. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10067-021-05807-3.