Red blood cell casts in acute interstitial nephritis.

Area of Science:

• Nephrology
• Immunology
• Pathology

Background:

• Drug-induced kidney injury is a significant clinical concern.
• Hydralazine and hydrochlorothiazide are commonly prescribed antihypertensive medications.
• Red blood cell casts in urinalysis typically indicate glomerular pathology.

Observation:

• A patient on hydralazine and hydrochlorothiazide developed reduced glomerular filtration rate, positive antinuclear antibody, and RBC casts.
• Renal biopsy showed normal glomeruli but mild interstitial nephritis affecting distal tubules.
• Impaired acidification was noted, but concentrating ability remained normal.

Findings:

• The study demonstrates that tubulointerstitial disease can lead to the formation of RBC casts.
• This challenges the traditional view of RBC casts as solely indicative of glomerular disease.
• The specific etiology of the observed interstitial nephritis remains undetermined.

Implications:

• This expands the differential diagnosis for patients presenting with RBC casts.
• It highlights the importance of considering drug-induced tubulointerstitial nephritis in such cases.
• Further research is needed to elucidate the mechanisms of RBC cast formation in tubulointerstitial diseases.