**Core Concept**
Hemolytic uremic syndrome (HUS) and Henoch-Schönlein purpura (HSP) are related but distinct conditions characterized by the deposition of IgA immune complexes, leading to microvascular inflammation and potentially severe renal involvement. The frequency of renal involvement in HSP varies widely in the literature.

**Why the Correct Answer is Right**
The correct answer, **10% - 50%**, reflects the range of reported frequencies of renal involvement in HSP. This variability is due to differences in study populations, diagnostic criteria, and the sensitivity of renal function tests used to detect abnormalities. Renal involvement in HSP is often characterized by the deposition of IgA immune complexes in the glomeruli, leading to inflammation and potential impairment of renal function. The kidneys are affected in a subset of patients, and the frequency of renal involvement can be influenced by factors such as the severity of the disease, the presence of hypertension, and the use of corticosteroids.

**Why Each Wrong Option is Incorrect**
**Option A:** 80% is incorrect because it overestimates the frequency of renal involvement in HSP, which is typically reported to be much lower than this value.

**Option C:** >60% is incorrect because it overestimates the frequency of renal involvement in HSP, which is generally reported to be lower than this value.

**Clinical Pearl / High-Yield Fact**
In patients with HSP, the presence of hypertension, proteinuria, or hematuria is associated with an increased risk of renal involvement and potential progression to HUS. These findings highlight the importance of closely monitoring renal function in patients with HSP.

**Correct Answer:**
✓ Correct Answer: D. 1O% - 50%