A case of γ1-heavy chain deposition disease successfully treated with melphalan and prednisolone therapy.

Heavy chain deposition disease (HCDD) is characterized by glomerular and tubular deposition of non-amyloidotic monoclonal heavy chains without associated light chains. We describe a case of gamma1-HCDD who presented with nephrotic syndrome, microhematuria, and hypocomplementemia. Renal biopsy showed lobular and nodular glomerulosclerosis along with IgG and C3 deposition. Electron microscopy revealed electron-dense deposits on the glomerular and tubular basement membranes and mesangium. Congo red staining was negative. Staining was positive for IgG1 on glomerular and tubular basement membranes but negative for IgG2-4, kappa and lambda light chains. Staining for the constant heavy chain domains showed the deletion of the first constant heavy chain domain. Thus, we diagnosed gamma1-HCDD. She was considered to be early-stage HCDD because proteinuria and hematuria were not observed before the nephrotic syndrome onset. Melphalan and prednisolone (MP) therapy reduced proteinuria as well as improved renal function and complement levels. Although renal prognosis of HCDD is poor, aggressive chemotherapy with MP may be effective in early-stage HCDD patients.