A possible rare cause of renal failure in streptococcal infection.

To the best of our knowledge, this is the first biopsy-proven case of streptococcal infection-associated acute interstitial nephritis (AIN) with existence of streptococcal pyrogenic exotoxin B (SPE B) by a controlled immunohistochemical method. Both the intact tubular epithelial cells and oedematous interstitium had strong positive signals, whereas only interstitial inflammation was dominant without tubular necrosis. Reflective of the nature of AIN is that the injury from the hypersensitivity reaction was specific for renal interstitium instead of tubules. SPE B is potentially allergenic and may confuse the clinicians due to its clinical mimicry of drug-induced AIN. Although very rare, AIN might be included into the differential diagnosis of patients with streptococcal sepsis and acute renal failure.