Women with spondyloarthritis occurring in the peripartum period develop a singular phenotype

BACKGROUND: Spondyloarthritis (SpA) has specific features in women and may be triggered by parturition. The peripartum period is marked by musculoskeletal remodelling and IL-17 secreting cell activation to enable childbirth. We therefore hypothesized that peripartum SpA might predominantly involve the entheses and be less dependent on HLA-B27 and TNFα. METHODS: We conducted a retrospective, observational, case-control study using the Rouen University Hospital's clinical data warehouse. Delivery dates and symptom onset were available for 154 women with SpA. Characteristics were compared between cases (with peripartum SpA) and controls. RESULTS: We identified 58 cases and 96 controls. HLA-B27 (37.3% vs. 52.3%, p-value: 0.04), anterior chest syndrome (74.1% vs. 54.7%, p-value: 0.012 and psoriasis (37.9% vs. 16.8%, p-value: 0.004 were significantly associated with peripartum SpA. Lower rates of biological inflammatory syndrome at TNFα inhibitor introduction, (22.2% vs. 48.1%, p-value: 0.003), of radiographic sacroiliac damage (4% vs. 18.6%, p-value: 0.012 and of MRI sacroiliitis (30.6% vs. 47.4%, p-value: 0.046 were observed in women with peripartum SpA. Also, a lower retention rate of TNFα inhibitors was observed in women with peripartum SpA, 45.6% at 12 months, versus 71.2% controls (Odd ratio: 2.56 [95% CI: 1.34-4.95]). Multivariate survival analysis found a hazard ratio for TNFα inhibitor discontinuation of 2.43 (95% CI: 1.62-3.65) within the first two years of treatment. CONCLUSIONS: Our study highlights a distinct phenotype of peripartum SpA, and a lower retention rate of TNFα inhibitors suggesting a worse response to these class of bDMARD. TRIAL REGISTRATION: As we conducted a retrospective study without health care intervention, no prospective registration was done.