A 29-year-old woman has had a fever and sore throat for the past 3 days. On physical examination, her temperature is 38degC. The pharynx is erythematous, with yellowish tonsillar exudate. She is treated with ampicillin and recovers fully in 7 days. Two weeks later, she develops fever and a rash and notices a slight decrease in urinary output. Her temperature is 37.7degC, and there is a diffuse erythematous rash on the trunk and extremities. Urinalysis shows a pH of 6; specific gravity, 1.022; 1+ proteinuria; 1+ hematuria; and no glucose or ketones. Microscopic examination of the urine shows RBCs and WBCs, including eosinophils, but no casts or crystals. What is the most likely cause of her disease?
An acute drug-induced interstitial nephritis can be caused by ampicillin. This is an immunologic reaction, probably caused by a drug acting as a hapten. Pharyngitis with post-streptococcal glomerulonephritis with deposition of immune complexes is unlikely to be accompanied by a rash or by eosinophils in the urine. Anti-glomerular basement membrane antibodies occur in Goodpasture syndrome, with hemorrhages in the lungs as well. Acute pyelonephritis is an ascending infection; it is uncommonly caused by the hematogenous spread of bacteria from other sites. Acute tubular injury can cause acute renal failure. It is caused by hypoxia resulting from shock or toxic injury caused by chemicals such as mercury, and only rarely, if ever, by bacterial toxins.
Deposition of immune complexes with streptococcal antigens
Formation of antibodies against glomerular basement membrane
Hematogenous dissemination of septic emboli
Hypersensitivity reaction to ampicillin
Kidney