An elderly patient with type 2 diabetes mellitus complicated with diabetic nephropathy and lupus nephritis

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We report a 76-year-old man with type 2 diabetes mellitus (DM) complicated with diabetic nephropathy and lupus nephritis. The patient had a 7-year history of DM without renal dysfunction. He was referred to our hospital for severe arthralgia and right chest pain. Laboratory examination indicated urinary granular casts, but not proteinuria. Systemic lupus erythematosus (SLE) was suspected based on symptoms and further laboratory findings such as serum autoantibodies including anti-DNA antibody, antinuclear antibody and perinuclear anti-neutrophil cytoplasmic antibody. Finally, renal biopsy revealed mesangial sclerosis, subendothelial deposit of electron dense material and necrotic vasculitis, which were interpreted as diabetic nephropathy and lupus nephritis, respectively. Treatment with oral prednisolone ameliorated serological abnormalities as well as clinical symptoms. These findings indicate that renal biopsy is indispensable for a definite diagnosis of nephropathy in diabetic patients without proteinuria but with active urine sediments.