Case Presentation: A 71 year old Caucasian man with uncontrolled diabetes mellitus, stage III chronic kidney disease, hypertension, hyperlipidemia, sick sinus syndrome, and osteomyelitis of the right 2nd metatarsal s/p amputation, was transferred from an outside hospital for evaluation of rash and acute on chronic kidney injury.
He first presented to the outside hospital for cellulitis of the right lower extremity with an abscess on his right first metatarsal. The abscess was drained and wound cultures grew methicillin sensitive staphylococcus aureus. Blood cultures did not show any growth and IV cefazolin was initiated. Due to a MRI-incompatible pacemaker, bone scan imaging was obtained, and findings were suggestive of osteomyelitis of the right first metatarsal head. The patient declined amputation and cefazolin was continued. The patient developed edema, a purpuric rash on his lower extremities, acute respiratory distress, lethargy, acute kidney injury, proteinuria, hematuria with red cell casts, and was transferred to our hospital for further care.

A skin biopsy of his rash demonstrated leukocytoclastic vasculitis and eosinophil deposition. Serology was significant for low C3 complement as well as elevated IgA and IgE levels. Renal biopsy revealed acute proliferative glomerulonephritis with C3 and IgA deposition on immunofluorescence microscopy and a diagnosis of staphylococcus-associated glomerulonephritis (SAGN) was established. The patient was discharged with a 6-week course of piperacillin-tazobactam and prednisone resulting in resolution of acute kidney injury and rash on follow-up.

Discussion: SAGN is an uncommon form of glomerulonephritis often seen in older, Caucasian men. Though inadequately studied, the proposed pathogenesis involves immune complexes, composed of staphylococcal antigens and the antibodies directed against them, that deposit in glomeruli when in circulation for a prolonged period. Patients present with lethargy, edema, hematuria with casts, proteinuria, and elevated creatinine, often with concurrent staphylococcus-associated endocarditis, skin infection or osteomyelitis. Cutaneous vasculitic symptoms can develop such as purpuric rash mimicking IgA vasculitis. A kidney biopsy showing C3 with IgG or IgA glomerular staining on immunofluorescence microscopy is diagnostic for SAGN. Bacterial eradication with resolution of systemic findings, hypocomplementemia, hematuria, and return of SCR to baseline are the focus of management.

Conclusions: PIGN has been predominantly referred to poststreptococcal glomerulonephritis. Though this form of PIGN is common in children, staphylococcus-associated glomerulonephritis should be suspected in adults presenting with rash, proteinuria, hematuria with casts, low C3 complement, and persistent AKI with concurrent, and not postinfectious, staphylococcus infection. Diagnosis is confirmed with renal biopsy and management is concentrated on staphylococcal eradication with antibiotics and source control.