**Question:** True about Henoch Schonlein purpura is-

A. It is a rare disease
B. It is caused by a viral infection
C. It typically affects children
D. It is characterized by abdominal pain, arthritis, and kidney involvement

**Correct Answer:** D. It is characterized by abdominal pain, arthritis, and kidney involvement

**Core Concept:** Henoch Schonlein purpura (HSP) is a systemic small vessel vasculitis affecting children. It is named after German physicians Emil Henoch and Moritz Schonlein. Although the disease can occur at any age, it most commonly affects children between 4 and 14 years old. HSP is characterized by four cardinal symptoms:

**Why the Correct Answer is Right:**
HSP presents with a characteristic clinical picture, called the "Four C's," which includes:

1. **C: Coagulopathy**: Hematuria (blood in urine), proteinuria (protein in urine), and renal involvement are common findings. This is because the small blood vessels in the kidneys are affected.
2. **C: Cutaneous**: Purpuric rash (reddish-purple discoloration of the skin) is the hallmark feature of HSP. It is typically located on the lower extremities and can progress to cover the entire body.
3. **C: Calf pain**: Intense, migratory (moving) pain in the lower limbs is a common symptom of HSP. This is due to vasculitis (inflammation of blood vessels) in the small vessels of the skin and internal organs.
4. **C: Calf tenderness**: Tenderness and swelling are also common symptoms of HSP. This is related to the inflammation of blood vessels, leading to increased permeability and fluid leak into the surrounding tissues.

**Why Each Wrong Option is Incorrect:**

A. False: Henoch Schonlein purpura is not a rare disease. It affects around 2-10 cases per 100,000 children per year, making it relatively common.
B. False: Viral infections are not the primary cause of HSP. The exact etiology is unknown, but it is believed to be an immune-mediated disease triggered by an infection, most often by a virus.

Ensure to understand the clinical features of Henoch Schonlein purpura and its differential diagnosis is crucial for accurate diagnosis and management.

**Clinical Pearls and Pearls:**

- Henoch Schonlein purpura is primarily a pediatric disease but can also occur in adults.
- The disease is more common in boys than girls and presents during warm seasons.
- In adult-onset HSP, it is often associated with systemic manifestations and may signal a more severe disease course.
- Diagnosis is typically made based on clinical presentation and exclusion of other causes of purpura such as vasculitis and thrombotic microangiopathy.