Acute poststaphylococcal glomerulonephritis superimposed on diabetic glomerulosclerosis

A 67-year-old Caucasian male presented with a 1-week history of productive cough and shortness of breath. He was found to have left lower lobe pneumonia, was admitted to the hospital, and was started on antibiotics. He developed acute renal failure shortly after admission with an increase in serum creatinine from 1.4mg/dl (124 mu mol/l) on hospital day 1 to 2.0 mg/dl (177 mmol/l) on day 4 to 7.0mg/dl (619 mmol/l) on day 20. Past medical history was significant for diabetes mellitus type II for 7 years with neuropathy, but without diabetic retinopathy. He also had history of coronary artery disease status-post coronary artery bypass graft, mitral valve regurgitation status-post replacement, atrial fibrillation, longstanding hypertension that was well-controlled on medications, and chronic renal insufficiency with a baseline serum creatinine of 1.4 mg/dl (124 mmol/l). He denied alcohol or IV drug use. He had no family history of renal disease. His medications on admission included furosemide, low dose aspirin, coumadin, glyburide, and metoprolol. He had 1+ lower extremity edema bilaterally. There were no cutaneous findings. Laboratory results during hospitalization were as follows: hematocrit 38%, white blood count 14 600/mm(3) (normal range 4300-10 800/mm(3)), platelets 243 x 10(9)/l (normal range 150-500 x 10(9)/l), urine protein 150 mg/ day, and serum albumin 3.6 g/dl (36 g/l) (normal range 3.5-4.9 g/dl (35-49 g/l). He had normal serum electrolytes, a depressed C3 complement level, and normal C4. All other serologies were negative or normal including anti-nuclear antibody, anti-double-stranded DNA antibody, hepatitis B surface antigen, hepatitis C antibody, antistreptolysin O antibody, serum cryoglobulin, antineutrophil cytoplasmic antibody, and anti-glomerular basement membrane (GBM) antibody. There was no M spike on serum protein electrophoresis. Urinalysis showed trace protein, numerous red blood cells/high-power field (hpf), 5-10 white blood cells/hpf, and several red blood cell casts. Sputum and blood cultures were positive for methicillin-resistant Staphylococcus aureus. Urine culture was negative. Chest X-ray showed consolidation of the left lower lobe of lung. The kidneys were normal in size by ultrasound. Hemodialysis was initiated and a renal biopsy was performed on hospital day 20.