1. Introduction
Monoclonal gammopathy is associated with various types of renal
injuries, such as light chain cast nephropathy (LCPT), AL amyloidosis,
and monoclonal immunoglobulin deposition disease, recently recognized as
monoclonal gammopathy of renal significance (MGRS). LCPT is a rare type
of MGRS, with approximately only 150–200 cases reported in the
literature [1–6]. In LCPT, monoclonal light chains secreted by
abnormal plasma cells accumulate in the proximal tubular cells and cause
proximal tubular dysfunction, which is clinically characterized by
tubular acidosis, normoglycemic glycosuria, aminoaciduria, and
hypophosphatemia, collectively called Fanconi syndrome [7].
Diagnosis of LCPT is confirmed by findings of renal biopsy and the
presence of specific histological features, including cytoplasmic
monoclonal light chain inclusions and an increased number of lysosomes
in the proximal tubular cells, which are sometimes only detectable by
electron microscopy [8]. In addition, the coexistence of LCPT and
other paraprotein-related kidney disease has been reported [9–11],
which makes the diagnosis more difficult. LCPT often presents as a
slowly progressive renal impairment; however, some patients develop
end-stage kidney disease or aggressive multiple myeloma [7].
Although the treatment strategy for MGRS has not yet been established
due to the rarity and lack of familiarity of this entity, several
studies have shown that improvement in renal function can be achieved
with hematologic response to chemotherapy, commonly bortezomib for
plasma cell dyscrasia, and rituximab for B cell lymphoproliferative
disease. Some case reports and case series have shown that chemotherapy
directed at multiple myeloma is also effective for LCPT [1–4], but
only a few case reports have described its clinical course, and the
optimal treatment strategy remains unknown.
Herein, we describe the case of a patient with LCPT and severe kidney
injury who received bortezomib-based chemotherapy and autologous stem
cell transplantation (ASCT). This case report illustrates new insight
into the optimal treatment strategy for LCPT in the future.