In PAN, cysts are seen in all except
**Question:** In PAN (Polyarteritis nodosa), cysts are seen in all except
A. Brain
B. Heart
C. Lung
D. Liver
**Correct Answer:** D. Liver
**Core Concept:** Polyarteritis nodosa (PAN) is a rare, necrotizing vasculitis affecting small and medium-sized arteries, typically in a segmental or lobar pattern. It can cause a wide range of clinical manifestations due to the involvement of various organs and systems. In PAN, cysts are a characteristic feature seen in various organs.
**Why the Correct Answer is Right:** Cysts are not typically found in the liver in PAN. Liver involvement is usually characterized by hepatitis-like symptoms, elevated liver enzymes, and occasionally portal hypertension. On the other hand, the correct answer (liver) is specifically excluded due to the absence of cysts in this organ.
**Why Each Wrong Option is Incorrect:**
A. Brain: Cysts are not typically seen in PAN affecting the brain, as it primarily affects the peripheral nervous system and can cause neurological symptoms.
B. Heart: Although PAN can involve the heart, cysts are not a characteristic feature of involvement in this organ. Heart involvement in PAN can lead to arrhythmias, valvular dysfunction, or myocardial damage.
C. Lung: Cysts are commonly seen in PAN affecting the lungs, which can manifest as hemoptysis, cough, or respiratory distress due to parenchymal involvement.
**Clinical Pearl:** Cyst formation is a characteristic feature of PAN affecting various organs, including the kidney, spleen, and skin. However, the absence of cysts in the liver distinguishes PAN from other conditions like autoimmune hepatitis, which can also present with elevated liver enzymes and hepatitis-like symptoms but has characteristic histopathological features.
Polyarteritis nodosa is a vasculitis that targets small and medium-sized arteries, causing inflammation and necrosis of the affected vessel walls. In PAN, the involvement of different organs can lead to diverse clinical manifestations, making it essential for clinicians to consider this entity in the differential diagnosis when evaluating patients with unexplained hepatitis-like symptoms and elevated liver enzymes.