[The 474th case: anemia, ostealgia, proteinuria].

A 49-year-old woman was admitted to hospital with intermittent dizziness and fatigue for 7 years. The symptoms were aggravated and accompanied by bone pain for more than 4 months. She was referred to our hospital. Laboratory tests and imaging findings suggested that acquired Fanconi Syndrome (FS) was associated with smoldering multiple myeloma (MM). Renal biopsy and electron microscopy confirmed the diagnosis of proximal light chain tubular disease (LCPT). LCPT causes proximal tubular dysfunction, which is characterized by the cytoplasmic crystal deposition usually kappa monoclonal light chain in the proximal tubule. MM with FS and LCPT is less common in clinical practice because it is difficult to diagnose. This is a typical case focusing on the differential diagnosis of monoclonal gammopathy of renal significance(MGRS) such as LCPT and plasma cells diseases.