Kidney transplant outcomes in patients with complement dysregulation.

backgroundComplement dysregulation is a key mechanism underlying atypical hemolytic uremic syndrome and complement-mediated thrombotic microangiopathy in kidney transplantation, and is associated with post-transplant recurrence, graft dysfunction, and graft loss. Although Western cohort data are well established, integrated transplant outcome data combining genetic analysis, anti-factor H (AFH) antibody profiling, and individualized therapy from Indian and other South Asian populations remain limited, despite a distinct biologic profile in this region.

aimTo evaluate clinical characteristics, complement biologic profile, post-transplant recurrence, and graft outcomes in kidney transplant recipients with complement dysregulation managed at a tertiary transplant center in Central India, with particular emphasis on genotype-phenotype correlation and outcomes in a resource-constrained setting.

methodsThis single-center retrospective cohort study included kidney transplant recipients with evidence of complement dysregulation identified from January 2018 to March 2025 at a tertiary transplant center in Central India. Complement dysregulation was defined as the presence of a pathogenic or likely pathogenic complement gene variant, AFH antibody positivity, or both. Genetic testing was performed using multiplex ligation-dependent probe amplification and/or clinical exome sequencing covering the alternative complement pathway gene panel, and AFH antibodies were measured using enzyme-linked immunosorbent assay. All patients underwent comprehensive evaluation including hematological, biochemical, and complement (C3, C4) profiling, with kidney biopsy when clinically feasible. The primary outcome was post-transplant recurrence of thrombotic microangiopathy; secondary outcomes included graft loss, patient survival, renal function, and treatment response. Median post-transplant follow-up was approximately 12 months.

resultsOf the 335 patients evaluated for complement abnormalities, 136 had complement dysregulation, of whom 38 underwent kidney transplantation and constituted the study cohort. Mean age was 36.3 ± 9.3 years, 84.2% were male, and 97.4% had hypertension; 73.7% were on maintenance hemodialysis at diagnosis. Complement genetic abnormalities were identified in 34/38 recipients (89.5%), with CFHR1-CFHR3 structural variants predominating (78.9%) and complement factor H abnormalities in 18.4%; no pathogenic variants were detected in

conclusionIn this Indian transplant cohort with complement dysregulation, CFHR1-CFHR3 structural variants and AFH antibody positivity defined the predominant biologic substrate, post-transplant recurrence clustered within the early weeks after transplantation, and disease-directed therapy with plasma exchange, rituximab, and selective eculizumab achieved durable graft preservation despite limited access to long-term complement inhibition. Comprehensive pre-transplant complement evaluation and biologic risk stratification are essential for safe transplantation in complement-mediated kidney disease, particularly in resource-limited settings.