Noncrystalline light-chain proximal tubulopathy: a retrospective study from a single institute of China

Light-chain proximal tubulopathy (LCPT) is a rare disease, which is classified as crystalline or noncrystalline based on the cytoplasmic inclusions in the proximal tubules. This study aimed to investigate the clinical features of noncrystalline LCPT from a single institute of China. We retrospectively enrolled patients diagnosed with isolated noncrystalline LCPT by kidney biopsy at Peking University First Hospital between 2011 and 2024. We systematically analyzed clinical data, kidney pathological type, treatment and prognosis. Twenty patients were enrolled. The mean age at diagnosis was 58 ± 12 and the sex ratio was 4/16 (female/male). Mean proteinuria was 1.9 ± 2.3g/24 hr and the mean estimated glomerular filtration rate (eGFR) at the point of biopsy 57 ± 30 mL/min/1.73 m². κ-light chain restriction (70%) was dominant among patients with noncrystalline LCPT. An abnormal serum free light chain ratio was detected in 50% of the patients. Proximal tubulopathy without cytoplasmic inclusions/acute tubular injury (60%) was the most common type, followed by proximal tubulopathy with lysosomal indigestion/constipation (25%) and tubulopathy associated with interstitial inflammation reaction (15%). During follow-up, patients received bortezomib-based or R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) or a daratumumab-lenalidomide-dexamethasone combination (DRD) chemotherapy vs. supportive treatment only. The mean follow-up time was 24 ± 22 months. All patients showed improved or stable kidney function during the observation period. This represents the first case series detailing noncrystalline LCPT with distinct pathological subtypes in northern China. Chemotherapy targeting aberrant plasma cell clones might favor kidney outcomes in patients with noncrystalline LCPT.