The clinicopathological characteristics and outcomes of IgA nephropathy with predominant lambda or kappa light-chain...

IgA nephropathy (IgAN) patients with monoclonal light-chain deposition may be at potential risk of hematological progression. However, whether the clinical characteristics of the patients with predominant lambda or kappa light-chain deposition were consistent with monoclonal light-chain deposition is limited to anecdotes.

We retrospectively studied patients in whom immunofluorescence showed IgA-alone deposits (n = 617) between January 2016 and January 2020. We divided the patients into two groups, the predominant lambda or kappa light-chain deposition group and the control group. Predominant lambda or kappa light-chain deposition was defined as the deposition intensity of kappa or lambda being + - and the other deposition intensity being ≥ 2 + .

Nineteen patients had predominant lambda or kappa light-chain deposition. The patients had a median age of 32 years. The median proteinuria was 0.9 g/day. The median eGFR was 79.8 ml/min per 1.73 m². Two patients had a mildly abnormal FLC ratio, but serum immunofixation electrophoresis showed polyclonal immunoglobulin. Eighteen patients showed lambda light chain-dominated deposition. In electron microscopy, organized structures in dense deposits were not observed in all patients. Nine patients with proteinuria ≥ 1.0 g/day received corticosteroids and immunosuppressants. The median follow-up time was 21 months. The rate of proteinuria remission was 50%. The clinical and pathological characteristics and outcomes were not significantly different between the predominant lambda or kappa light-chain deposition group and the control group.

The result for IgAN patients with predominant kappa/lambda light-chain deposition seemed to be the same as that of IgAN patients with light-chain codeposition. However, as this was a single-center study with a small size, further multicenter studies and long-term follow-up are needed to confirm our findings.