Multiple myeloma-associated light chain proximal tubulopathy: a case report

Abstract

Abstract Background: Multiple myeloma (MM)-associated light chain proximal tubulopathy (LCPT) mainly damaged the proximal tubules, characterized by the deposition of cytoplasmic inclusions in the proximal tubules.The main lesions of LCPT were proximal tubular damage. Here, we report two cases of LCPT and analyze their pathologic characteristics to delineate the charateristics of clinical pathology and outcomes. Case presentation: A 55-year-old male patient (Case 1) and a 64-year-old male patient(Case 2)were referred to our hospital and diagnosed with MM-associated LCPT with crystalline(κ type) and with non-crystalline LCPT (λ type), respectively.The prominent morphologic feature of crystalline LCPT was the dark-brown granules,which could be detected by using Jones silver methenamine staining,in the proximal tubules through the electron microscopic examination.The typical morphologic-feature of the non-crystalline of LCPT was that the eosinophilic granules,which could be examined by using masson trichrome staining.Besides,an abundance of lysosome could be found by the electron microscopic examination in the non-crystalline of LCPT. The case 1 was treated with 27 cycles of chemotherapy and autologous stem cell transplantation. The treatment of case 1 was effective, and the renal was functioning stably at the 36 months of the follow-up. The case 2 was treated with 44 cycles of chemotherapy. The treatment of case 2 was ineffective. Given the function of case 2’s renal was worsing,dialysis was conducted at 30 months of follow-up. Conclusions: The morphologic lesions of proximal tubular damage in LCPT is quite variable.Renal biopsy is the first choice for the accurate diagnosis of LCPT. Besides, the clinicopathological features of LCPT are also crucial for accurate pathologic diagnosis and personalized treatment.