Belimumab-induced remission in refractory lupus mesenteric vasculitis: a case report with 49-month follow-up.

Background: Lupus mesenteric vasculitis (LMV) is a rare but life-threatening gastrointestinal complication of systemic lupus erythematosus (SLE). Refractory cases pose significant therapeutic challenges due to limited treatment options and cumulative toxicity from long-term immunosuppressant therapy. Case presentation: A 46-year-old woman with SLE presented with recurrent abdominal pain, diarrhea, and malar rash over a 1-year period. Despite receiving standard immunosuppressive therapies-including glucocorticoids (GCs), cyclophosphamide, mycophenolate mofetil, and tacrolimus-she experienced multiple relapses of LMV between 2015 and 2020, confirmed by abdominal computed tomography showing bowel wall thickening and the characteristic "target sign." In September 2020, belimumab (600 mg intravenous every 4 weeks) was initiated alongside a reduced-dose GC regimen. Over a 49-month treatment period (34 doses), the patient achieved sustained remission, with complete resolution of abdominal symptoms, normalization of computed tomography findings, stable Systemic Lupus Erythematosus Disease Activity Index scores (0-4), decreasing anti-double-stranded DNA titers (<20 IU/mL), and rising serum complement C3 levels (>0.6 g/L). GC dosage was successfully tapered to 2.5 mg/day without disease relapse. Conclusions: This case demonstrates belimumab's efficacy in achieving the longest documented remission (49 months) in refractory LMV, highlighting its potential as a first-line biologic for steroid-dependent gastrointestinal vasculitis.