Minimal Change Disease and Overlapping IgA Nephropathy Associated with Peripheral Inflammatory Spondyloarthropathy

Introduction: Spondyloarthritis (SpA) describes a group of seronegative rheumatic disorders that cause skeletal inflammation. They are often associated with HLA-B27 and have been linked with kidney disease, specifically IgA nephropathy. However, associations between SpA and other glomerular diseases have not been well elucidated. Here, we present a rare case of minimal change disease (MCD) associated with peripheral SpA. Case Description: A 50-year-old male with HTN presented with AKI and nephrotic syndrome with Cr 2.9mg/dL and urine protein creatinine ratio (UPCR) 18.6g/g. A few months prior, he developed right knee pain treated with NSAIDs. Kidney biopsy revealed MCD with mild IgA nephropathy. He was treated with prednisone 1 mg/kg daily for 4 weeks until remission was achieved. After a 4-month taper, he developed severe pain and stiffness of multiple distal joints. Labs notable for CRP 86.7 mg/L and UPCR 7.5g/g. Further workup included positive HLA-B27 and synovial fluid analysis consistent with inflammatory arthritis, raising suspicion for peripheral SpA. Prednisone was resumed, and his joint symptoms and proteinuria subsequently resolved. Unfortunately, due to recurring arthritic flares at lower steroid doses, prednisone could not be tapered. Methotrexate was initiated without response. Then, adalimumab was initiated and steroids were tapered off. Over 2 months, CRP and UPCR normalized, arthritis symptoms resolved, and MCD remission was achieved. Discussion: Kidney involvement is seen in many rheumatic diseases, whether from direct pathologic effect or secondary to treatment. Nephrologists and rheumatologists must work together to manage these patients. SpA with HLA-B27 positivity has previously been linked with kidney disease, specifically ankylosing spondylitis and IgA nephropathy. Our patient with primary MCD associated with peripheral SpA is discordant with existing literature. His joint symptoms were primarily peripheral, unlike ankylosing spondylitis, and there was no clinical evidence to suggest reactive arthritis or arthritis associated with psoriasis or IBD. With adalimumab, his joint symptoms and proteinuria quiesced. This case emphasizes the temporal relationship between MCD and peripheral SpA. Recognizing the interconnection between the diseases played a key role in successfully treating this patient.