**Core Concept**
Henoch-Schönlein purpura (HSP) is a form of vasculitis that affects small blood vessels, characterized by the deposition of IgA immune complexes. It typically presents with a classic tetrad of symptoms: non-thrombocytopenic purpura, abdominal pain, arthritis, and renal involvement.

**Why the Correct Answer is Right**
HSP is most commonly seen in children, with a peak incidence between 3 to 6 years of age. This age group is more susceptible to the condition due to the immaturity of their immune system and the higher levels of IgA antibodies. The exact pathophysiology involves the deposition of IgA immune complexes on the endothelial surface of small blood vessels, leading to inflammation and damage.

**Why Each Wrong Option is Incorrect**
**Option A:** Adults are less commonly affected, although it can occur in any age group, especially in individuals with underlying systemic diseases or immunocompromised states.
**Option B:** While HSP can present atypically, the classic age group remains between 3 to 6 years of age, making this option incorrect.
**Option C:** Although HSP can involve the kidneys, this option is too specific and does not address the age group typically affected.

**Clinical Pearl / High-Yield Fact**
Remember the classic tetrad of HSP symptoms: non-thrombocytopenic purpura, abdominal pain, arthritis, and renal involvement. This can help differentiate HSP from other vasculitic conditions.

**Correct Answer:** C. Children.