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Background and Aims Kidney diseases with heavy chain deposition are rare, including AHL amyloidosis also. The mutation/deletion of the constant domain (CH1/CH2) of the heavy chain causing high tissue affinity seems most likely in its pathogenesis. The very low serum level is responsible for the difficult diagnosis, which is often based on kidney biopsy or laser microdissection / mass spectrometry. Method Case study of a 76-year-old male patient, examined in January, 2019. Results Besides treatment for Ménière syndrome and benign prostatic hyperplasia there was no other important event in patient’s history. Significant proteinuria and microscopic haematuria were observed from May 2016, but eGFR was 70 ml/min/1,73 m2 at that time. By April, 2018 nephrotic range proteinuria (10 g/day) with full nephrotic syndrome developed. Screening tests for cancer were negative. Despite symptomatic treatment, half year later eGFR decreased to 27 ml/min/1,73 m2, therefore he was referred to nephrology. Serum protein electrophoresis verified IgG lambda (8,1 g/l) and free lambda (0,5 g/l) monoclonal light chains, and in addition the possibility of IgG heavy chain accumulation. Urine electrophoresis showed also IgG lambda (1720,1 mg/l), and free lambda light chain (552,1 mg/l) monoclonality. Serum free lambda and kappa light chain ratio was 0,06, complement serology was normal. Kidney biopsy was done, which showed IgG heavy and light chain restriction, Congo red stain positivity and apple green birefringence under the polarized microscope in the expanded mesangium, in the interstitium and along the tubular basement membrane and the blood vessels. The electron microscope detected fibrillary deposits (10 nm) in the same structures, therefore diagnosis of AHL amyloidosis was established. He had no extrarenal symptoms. Bone marrow aspiration flow cytometry verified 1,11% plasma cell accumulation, 93% of them had pathological immunphenotype. Bone marrow morphology assay showed 30-40% plasma cell infiltration, and chromosome assay detected monoallelic deletion of IgH and MAF and gains of 1q region, suggesting myeloma multiplex in the background of AHL amyloidosis. VCD (bortezomib-cyclophosphamide-dexamethason) treatment was started, so far he has received 8 cycles. He is asymptomatic, proteinuria decreased, kidney function stabilized, eGFR 23 ml/min/1,73 m2. Conclusion only about 20 cases of AHL amyloidosis have been reported in the literature so far. In the context of longstanding kidney failure with nephrotic syndrome, we should consider renal disease associated with plasma cell dyscrasia also. If case of an AHL amyloidosis caused by myeloma multiplex, effective anti-plasma cell therapy can improve the hematological and the renal outcome.