Combined IgG4κ and IgG1λ Deposition in the Glomerular and Tubular Basement Membrane Accompanied by Autoimmune Neutropenia (AIN) and Immune Thrombocytopenia (ITP)

A 48-year-old male was admitted to our hospital with nephrotic syndrome. Light-microscopic examination of a renal biopsy specimen showed almost normal glomerular appearance, however, immunofluorescence examination revealed linear and granular IgG deposits on the glomerular basement membrane (GBM), accompanied by slight IgG deposition in the tubular basement membrane (TBM). Further investigation of the IgG subclass and light chain staining revealed that the glomerular deposits were composed of IgG1 and IgG4, with both κ and λ light chains, while the tubular deposits were composed of only IgG4 and κ light chains. The electron-microscopic findings of small granular deposits in the GBM and TBM closely resembled those of light and heavy chain deposition disease (LHCDD). Immunoelectron microscopy confirmed the presence of κ and λ chains in the GBM and TBM, however, only significant κ chain deposition was found in the TBM. There was no evidence of monoclonal gammopathy. Clinically, the patient subsequently developed neutropenia and thrombocytopenia associated with the presence of anti-neutrophil antibody and anti-GPIIb/IIIa antibody-producing B cells in the blood. Oral steroid administration was initiated, which led to amelioration of the neutropenia, thrombocytopenia and proteinuria. This may be a very rare case of combined IgG4κ and IgG1λ deposition disease accompanied by autoimmune neutropenia (AIN) and immune thrombocytopenia (ITP) suggestive of biclonal immunoglobulin deposition disease (BIDD). Investigation of the IgG subclass and of the light chains was useful for recognizing the clonality of the immunoglobulin deposits in the kidney.