In our Clinical Problem-Solving series, information about a real patient is presented in stages to an expert clinician, who responds to the information, sharing his or her reasoning with the reader. The latest article, Bitter Pills, was first presented as an Interactive Medical Case, giving readers the opportunity to test their diagnostic skills.
• What is the classic triad associated with tubulointerstitial nephritis?
The classic triad of fever, peripheral eosinophilia, and rash is present in only a fraction (approximately 10%) of patients with allergic tubulointerstitial nephritis, although at least one of these features is present in the majority of cases.
• What urinary findings are typical in patients with tubulointerstitial nephritis?
Giemsa staining of a cytospin preparation of urinary sediment shows lymphocytes, plasma cells, and eosinophils in cases of acute tubulointerstitial nephritis. The presence of eosinophils in urine can be helpful in suggesting the diagnosis and can be detected with the use of Wright, Giemsa, or Hansel staining; however, the positive and negative predictive values of this finding are low. White-cell casts or red-cell casts would point to a diagnosis of acute tubulointerstitial nephritis or glomerulonephritis.
Morning Report Questions
Q: What are the most typical causes of tubulointerstitial nephritis?
A: The causes of tubulointerstitial nephritis include drug-induced allergic reactions, infection, autoimmune inflammation (e.g., systemic lupus erythematosus and Sjogren’s syndrome), and the syndrome of tubulointerstitial nephritis and uveitis. Medications account for about 70% of cases.
Q: How should allergic interstitial nephritis be managed?
A: The initial approach to the treatment of allergic interstitial nephritis is to remove the offending agent. Conclusive data are lacking to support the use of immunosuppressants as adjunctive therapy. The findings in retrospective case series have been inconsistent.