A 7 year old male had non blanching rashes over the shin and swelling of knee joint with haematuria +++ and protein +. Microscopic analysis of his renal biopsy specimen is most likely to show?
**Core Concept**
The clinical presentation suggests a diagnosis of **Henoch-Schönlein Purpura (HSP)**, a form of vasculitis that affects small blood vessels and is characterized by **non-blanching rashes**, **arthritis**, **gastrointestinal symptoms**, and **renal involvement**. The underlying pathophysiology involves the deposition of **immune complexes** containing **IgA antibodies**.
**Why the Correct Answer is Right**
The correct answer is related to the characteristic renal biopsy findings in HSP, which typically show **mesangial IgA deposition** and **proliferative glomerulonephritis**. This is due to the immune complex-mediated inflammation that affects the glomeruli, leading to **hematuria** and **proteinuria**. The presence of **IgA deposits** in the mesangium is a hallmark of HSP nephritis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically relate to the characteristic immune complex deposition seen in HSP.
**Option B:** This option is also incorrect as it does not accurately describe the typical renal biopsy findings in HSP.
**Option C:** This option is incorrect because it is more characteristic of other types of glomerulonephritis.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that HSP is the most common form of vasculitis in children, and renal involvement is a common complication. The presence of **palpable purpura**, **abdominal pain**, and **arthritis** should raise suspicion for HSP.
**Correct Answer:** D. Mesangial IgA deposition.