Unusual manifestation of crystalline light chain tubulopathy in patient with multiple myeloma: case report and review of the literature

Abstract

Multiple myeloma (MM) is the second most common hematological malignancy, with an annual incidence in Europe and the USA of about 4–6 cases per 100,000. Several forms of renal disease are found in the course of MM, including: cast nephropathy, light chain (LC) deposition disease and primary amyloidosis. Less frequent forms include: acute and chronic tubulopathies, neoplastic plasma cell infiltration and interstitial nephritis. In this paper, we discuss a case of 53-year-old male patient with MM who presented with massive proteinuria (24 g/24 h), mild renal insufficiency (eGFR 43 mL/min), and Fanconi-like syndrome (as reflected by normoglycemic glycosuria). In kidney biopsy glomeruli were normal, whereas abundant AFOG-positive deposits were found in the cytoplasm of proximal tubular epithelial cells. These deposits were strongly positive for kappa light chains on immunofluorescence. Electron microscopy revealed electron-dense, intracytoplasmic crystalloid deposits of variable shape (needle-shaped, round and rectangular), and size in the proximal tubular cells. This unusual variant of microscopic renal lesions in the course of MM coupled with coincidence of Fanconi-like and nephrotic syndrome as a clinical manifestation has not been reported to date.

• Chronic kidney disease
• crystalline nephropathy
• fanconi syndrome
• multiple myeloma
• nephrotic syndrome