Question

Consider the following statements regarding classic polyarteritis nodosa:
1. It is multi-system necrotising vasculitis
2. Small and medium vessels are involved
3. Pulmonary artery involvement is a characteristic feature
4. Up to 30% patients may test positive for Hepatitis B surface antigen.

Which of these statements are correct?

• A. 1 and 2
• B. 2 and 3
• C. 1, 2 and 4
• D. 2, 3 and 4

Hint:

Remember which organ classic PAN is taught to spare.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
Four statements about classic polyarteritis nodosa (PAN) are given, and we need to work out which of them are actually true.

Step 2: Key Formula or Approach:
Classic PAN is defined as a necrotising vasculitis of medium and small sized muscular arteries, sparing arterioles, capillaries and venules, and it typically spares the lungs. Knowing this definition lets us check each statement one at a time.

Step 3: Detailed Explanation:
Statement 1 says it is a multi-system necrotising vasculitis. This is correct, since PAN can affect vessels supplying the kidney, gut, nerves, skin, muscles and other organs together.
Statement 2 says small and medium vessels are involved. This is also correct, since classic PAN affects medium sized muscular arteries and can extend to small arteries, though it spares arterioles, capillaries and venules.
Statement 3 says pulmonary artery involvement is a characteristic feature. This is incorrect. A key teaching point about classic PAN is that it characteristically spares the lungs, unlike diseases such as microscopic polyangiitis or granulomatosis with polyangiitis. Lung involvement argues against classic PAN.
Statement 4 says up to 30% of patients test positive for Hepatitis B surface antigen. This is correct and a well known association, since PAN can be triggered by chronic Hepatitis B infection, with immune complex deposition in vessel walls.
So the correct statements are 1, 2 and 4, while statement 3 is false.

Step 4: Final Answer:
The correct combination is statements 1, 2 and 4, since classic PAN is multi-system, affects small and medium vessels, is linked with Hepatitis B in up to 30% of cases, but does not characteristically involve the pulmonary artery.