Clinical characteristics and prognosis of IgA nephropathy with predominant light chain deposition

To compare the clinicopathological features, treatment response, and renal outcomes of patients with IgA nephropathy (IgAN) with κ-dominant, κ-λ co-deposition, or λ-dominant light-chain deposition. This retrospective, single-centre cohort study included 105 patients with primary IgAN who underwent their first native-kidney biopsy. Twenty-one patients with κ-dominant deposition were matched to 42 patients with κ-λ co-deposition and 42 patients with λ-dominant deposition based on age, sex, 24-hour urinary protein excretion, and baseline serum creatinine. The final matching ratio was 1:2:2. The primary renal endpoint was a sustained ≥30% increase in serum creatinine from baseline. During a median follow-up of 25 months (IQR, 18-36), 21 patients reached the renal endpoint. Time to treatment response did not differ significantly among the three groups (log-rank p = 0.0707). However, renal progression-free survival differed significantly among the light-chain deposition groups (log-rank p = 0.0046). After adjustment for sex, age, 24-hour urinary protein excretion, and baseline eGFR, a higher κ deposition ratio remained associated with a lower hazard of renal progression (HR [per 1-percentage-point increase] 0.96; 95% CI: 0.94-0.99; p = 0.011). A higher κ light-chain deposition ratio was associated with a lower risk of renal progression in IgAN. κ predominance may be a pathological marker of a distinct and possibly less aggressive immune-complex deposition pattern.