RESPONSE TO HYDROXYCHLOROQUINE IN IMMUNE THROMBOCYTOPENIA IN CHILDHOOD-ONSET SLE

PV166 / #638 Poster Topic: AS18 - Pediatric SLE Background/Purpose The management of immune thrombocytopenia in childhood-onset systemic lupus erythematosus (cSLE) is diverse and yet to be standardized. We aimed to analyze the efficacy and safety of hydroxychloroquine (HCQ) in the treatment of thrombocytopenia (platelet count <100× 10^9/L) associated with cSLE. Methods We retrospectively reviewed the medical records of patients who developed thrombocytopenia (platelet count <100 × 10^9/L) and were followed in the SLE clinic at The Hospital for Sick Children, between January 2015 and December 2022. Definite cSLE was defined by ANA titer ≥ 1:160 measured by immunofluorescence and ≥10 points according to the 2019 EULAR/ACR 2019 classification criteria, while patients with incipient cSLE were ANA positive, had clinical features of evolving SLE but achieved a score below 10. Complete response was defined as a platelet count >100 x 10^9/L with no bleeding. Partial response was defined as a platelet count >30 x 10^9/L with at least a 2-fold increase of the baseline count and no bleeding. Qualitative data were analyzed using descriptive statistics. Results Of the 265 patient records reviewed (201 with definite cSLE and 64 with incipient cSLE), 55 (21%) patients had thrombocytopenia (Table 1). Nine patients with thrombocytopenia secondary to other causes, such as medications related or infections, were excluded. Forty-six patients (70% female), with a median age of 12.9 years (IQR 10.6 - 14.9) and median platelet count of 16.5 × 10^9/L (IQR 6 - 61) at time of thrombocytopenia diagnosis were included. The median lowest platelet count was 6 × 10^9/L (IQR 2 - 31). Twenty-eight (61%) patients had definite cSLE, while 18 (39%) had incipient cSLE. Median SLEDAI score at cSLE diagnosis (for definite SLE) was 7 (IQR 5 - 12). Thirty-one (67%) patients were treated with corticosteroids and/or IVIG prior to commencing HCQ, and 10 of them (22%) also required 1 or more additional treatments for thrombocytopenia (ie, azathioprine, mycophenolate mofetil, eltrombopag, romiplostim, rituximab, or cyclophosphamide). Thirteen (28%) patients achieved either a complete or partial response prior to initiating HCQ. Forty-one (89%) patients were treated with HCQ during their disease course. HCQ was initiated at a median of 6 months (IQR 2.7-12.2) after thrombocytopenia diagnosis at a median platelet count of 65 × 10^9/L (IQR 19-131). Twenty-six (63%) of the patients treated with HCQ had a complete or partial response at 12 weeks after initiating HCQ. Fourteen (34%) patients required additional treatment for thrombocytopenia during this time. Forty-three (93%) patients had either complete (n=39) or partial response (n=4) after 1 year and/or at the end of follow-up, including 38 (93%) who received HCQ. The median follow-up time was 27 months (IQR 12.7-52). At the end of follow-up, only 3 patients required a second drug (either sirolimus, eltrombopag, mycophenolate mofetil, or azathioprine). Only 1 patient discontinued HCQ due to side effects (headache). Table 1. Demographics of Patients Included In Analysis Conclusions In a cohort of children with definite or incipient cSLE, we observed successful management of thrombocytopenia on HCQ monotherapy nearly 2 years after their onset, although two-thirds required immunosuppression at presentation. Further analysis will identify characteristics that predict response to HCQ monotherapy.

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