A case of crystalglobulin-induced nephropathy wherein M protein was identified by mass spectrometry and immunoglobulin G subclass staining.

Crystalglobulin-induced nephropathy is a rare disease that causes the deposition of crystallized monoclonal immunoglobulins into the glomerular capillary and arteriole spaces. Here, we report the case of a patient who presented with skin ulcers, urinary protein, and renal dysfunction. The patient underwent renal and skin biopsies, and the biopsy tissue samples were subjected to mass spectrometry. The patient was diagnosed with crystalglobulin-induced nephropathy. A literature review suggested that pathological examinations using electron microscopy, mass spectrometry, and immunofluorescent staining of paraffin-embedded biopsy samples treated with pronase may be useful for the diagnosis of this condition.