A RARE COEXISTENCE OF C3 GLOMERULOPATHY AND SYSTEMIC LUPUS ERYTHEMATOSUS IN A YOUNG FEMALE

The simultaneous occurrence of C3 glomerulopathy (C3G) and systemic lupus erythematosus (SLE) is rare, posing significant diagnostic and therapeutic challenges especially in low-income countries like the Philippines. C3 glomerulopathy is a rare, complement-mediated kidney disease with a reported incidence between 1 and 2 per million that is characterized by dysregulation of the complement cascade, leading to C3 deposits within the glomeruli. Conversely, SLE is an autoimmune disease characterized by multiorgan involvement. Very few reports exist in literature about the coexistence of both diseases, and to the best of our knowledge, only ten cases were reported globally as of the time of writing, with none from the Philippines. This case report details a patient diagnosed with SLE with exclusive findings of C3G on renal biopsy, along with her treatment, outcome, and follow-up.

This report discusses an unsual case of a 29-year-old Filipino female who presented with recurrent arthralgia, myalgia, fever, and oral ulcers. Her symptoms began a year earlier and included fatigue, edema, and photosensitive skin eruptions. Initial tests abroad revealed elevated anti-dsDNA, proteinuria, low C3 and C4, and positive anti-cardiolipin and anti-β2 glycoprotein antibodies. Kidney biopsy was consistent with C3 glomerulopathy. She was treated with prednisolone but was lost to follow-up. Her symptoms recurred and  laboratory results upon admission showed anemia; positive ANA, anti-dsDNA, and direct Coombs test; elevated serum creatinine and urine albumin/creatinine; low C3; normal C4; and microscopic hematuria.

Our patient was diagnosed with SLE by fulfillment of the 2019 EULAR/ACR and the 2012 SLICC criteria and with C3G by virtue of her renal biopsy result. Hydroxychloroquine, mycophenolate mofetil, enalapril, and methylprednisolone pulse therapy were initiated which resulted in low disease activity. There was improvement in proteinuria and stable creatinine during follow-up.

In addition to our case, very few reports exist in literature regarding the fortuitous association of C3G in association with SLE. The coexistence of both diseases is a rare clinical scenario, posing therapeutic challenges especially in low-income countries. There is no established optimal treatment for C3G, and while newer studies show that eculizumab suggests benefit for both diseases, it was not available locally. Similar to some of the previous reports, our patient was treated with methylprednisolone pulse therapy, hydroxychloroquine, mycophenolate mofetil, and enalapril, which resulted in low disease activity. There was improvement in proteinuria and stable creatinine during follow-up.

This rare case of C3G concurrent with SLE underscores the intricate interplay between autoimmune and complement-mediated renal pathologies. It highlights the necessity for comprehensive diagnostic approaches and personalized treatment strategies, especially in low-income countries like the Philippines where lack of medical infrastructure and scarce treatment options amplify the challenges presented by such overlapping conditions. Enhanced understanding of the pathophysiological mechanisms and continued research are essential for improving patient management and outcomes in these unique cases.

Disclaimer: This abstract was also submitted for the Asia-Pacific League of Associations for Rheumatology (APLAR) congress. By submitting the abstract to WCN'26, abstract authors declare that re-submitting the abstract is permitted by the organizers of the previous meeting.