A 46 year old patient with no past history of interest came to the emergency department with pain in the left teste radiating to the ipsilateral flank, without fever or accompanying micturition syndrome. Physical examination was unremarkable, except for arterial hypertension. Renal and testicular-prostatic ultrasound with no findings. Rapidly progressive deterioration of renal function (creatinine 9.79 mg/dl, 4.85 g/24 proteinuria without active sediment) and progressive anaemia (Hb 8.1 g/dl, mean corpuscular volume 88 fl, mean corpuscular haemoglobin 31.1, mean corpuscular haemoglobin concentration 35.4). Immunological study (antinuclear antibodies, anti-neutrophil cytoplasm antibodies, anti-GBM, anti-streptolysin, rheumatoid factor, C3-4), viral serology and tumour markers were normal. Proteinogram-immunofixation with immunoglobulin (Ig)A-kappa monoclonal band. IgG 317, IgA 1446, IgM 15 mg/dl, free light chain (FLC, Free-Lite® nephelometry) kappa 4090 ng/ml, lambda 1. Uric acid 10.8, LDH 269, calcium 10.2, albumin 3.3, B2-microglobulin 23340. Anatomopathological diagnosis was made of kappa light chain cylinder nephropathy (CLL-K) and Durie Salmon stage IIIB IgA-kappa MM, and treatment was started with bortezomib-dexamethasone, together with renal depurative therapy with Theralite® high cut-off filter every other day.

Over the following two months, serum IgA levels decreased progressively and significantly, but not pre-dialysis FLC-K, but it was decided in a multidisciplinary clinical session to continue with the treatment established according to the haematology protocol and to rebiopsy the kidney to assess the continuation of renal depurative therapy. The rebiopsy revealed chronic tubulointerstitial lesions of mild-moderate intensity, and 6 more cycles of high cut-off dialysis were prescribed.

Three months after diagnosis, after 4 cycles of chemotherapy, bortezomib was declared ineffective and was replaced by lenalidomide adjusted to renal function. Due to economic reasons, the continuation of FLC depurative therapy was not possible (having received a total of 18 sessions), and the patient remained on renal replacement therapy with conventional high-flux dialysis. The efficacy of lenalidomide is confirmed (Task Force, SWOG and EMBT), which the patient is on three years after diagnosis, in addition to renal replacement therapy.