Kidney transplant outcomes in patients with complement dysregulation

Complement 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.

To 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.

This 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.

Of 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 CFI, C3, CD46, THBD, or DGKE. AFH antibodies were detected in 15 patients (39.5%), with 11 having concomitant genetic abnormalities. Pre-transplant immunomodulation with plasma exchange and rituximab reduced mean AFH antibody levels from 179.9 AU/mL to 59.7 AU/mL (approximately 67% reduction). Post-transplant recurrence occurred in 7/38 recipients (18.4%), all biopsy-confirmed, donor-specific antibody and C4d-negative, and clustered within 1-3 weeks of transplantation; recurrence occurred exclusively in patients with complement genetic abnormalities, and not in those with isolated AFH antibody positivity. All 7 recipients with recurrence maintained functioning grafts after disease-directed therapy. Overall patient survival was 94.7%; two deaths (5.3%) were attributable to severe infections, and one graft loss followed invasive mucormycosis unrelated to recurrent disease.

In 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.