Henoch-Schonlein purpura-like presentation in IgA-dominant Staphylococcus infection-associated glomerulonephritis - a diagnostic pitfall

Background: In children and adults, Henoch-Schonlein purpura (HSP) has a characteristic clinical presentation that includes a purpuric lower extremity skin rash, IgA-dominant glomerulonephritis, and abdominal and joint pain. A similar clinical presentation can be seen in adults who have a systemic infection with methicillin-resistant Staphylococcus aureus. It is critically important to distinguish the IgA-dominant glomerulonephritis of HSP from the IgA-dominant glomerulonephritis of staphylococcal infection, because HSP may need to be treated with corticosteroids and immunosuppressives, while Staphylococcus infection-associated glomerulonephritis requires antibiotics. Design: We searched our renal biopsy database for cases of Staphylococcus infection-associated IgA-dominant glomerulonephritis, to identify those with an HSP-like presentation. Their clinical, laboratory, and biopsy findings are reviewed. Results: Between 2004 and 2011, we identified 37 patients with culture-proven Staphylococcus infection-associated glomerulonephritis. Of these, 8 (22%) had an HSP-like presentation manifested by lower extremity purpuric skin rash. Mesangial IgA and C3 deposits were consistent findings on kidney biopsy. Crescents were uncommon. Four of the 8 patients received glucocorticoid (steroid) therapy for a presumed diagnosis of HSP. Renal function worsened in 3 patients, and 1 patient ultimately improved but developed sepsis during the course. Overall, renal outcome was poor in 71% of the cases despite mild chronic renal injury in the biopsy. Conclusion: In adult patients with an HSP-like presentation, a high index of suspicion for underlying Staphylococcal infection is warranted. Blood cultures are frequently negative. Cultures from the site of infection should be performed. Steroid treatment did not improve outcomes. Renal outcomes were frequently poor.