Untreated polyarteritis nodosa is most likely to cause death due to involvement of which organ?

• A. Heart
• B. Lungs
• C. Brain
• D. Kidney

Answer: (D)

Polyarteritis nodosa is a systemic vasculitis of medium-sized arteries that often involves the renal arteries, leading to renovascular hypertension and progressive kidney failure. The kidneys’ critical role in filtering blood and regulating fluids and electrolytes means that renal ischemia and hypertension from arterial inflammation can rapidly progress to life-threatening renal failure if untreated. While other organs like the brain or heart can be affected, the characteristic and most deadly complication in untreated PAN is renal involvement, making the kidney the organ most likely to drive mortality. The lungs are typically spared in classic PAN, so pulmonary failure is less likely to be the fatal issue.