**Core Concept:** Chickenpox, caused by the varicella-zoster virus, is a common childhood infection characterized by a vesicular rash, fever, and systemic symptoms. While most children recover fully, complications can occur.

**Why the Correct Answer is Right:**
Complications of chickenpox in children can involve various organs and systems. One of the main complications is **Herpes zoster**, which is a reactivation of the varicella-zoster virus. In this case, the virus travels down sensory neurons to the dermatome and causes a localized dermatitis. The rash typically appears in a segmental pattern and is accompanied by regional pain, known as "postherpetic neuralgia."

**Why Each Wrong Option is Incorrect:**
A. **Infectious mononucleosis (glandular fever)** is a viral infection caused by the Epstein-Barr virus, not varicella-zoster virus. It presents with lymphadenopathy, hepatosplenomegaly, and pharyngeal inflammation, not typically causing dermatitis or postherpetic neuralgia.
B. **Measles** is another viral infection, caused by the measles virus, which presents with a similar rash but is not caused by the reactivation of the varicella-zoster virus.
C. **Infectious mononucleosis** can also cause fever, lymphadenopathy, and hepatosplenomegaly, but not herpetic dermatitis or postherpetic neuralgia.
D. **Measles** is a viral infection caused by the measles virus, which presents with a rash but is not caused by the reactivation of the varicella-zoster virus.

**Clinical Pearl:**
Herpes zoster (shingles) is a common complication of chickenpox in children, particularly when chickenpox is poorly managed or occurs in immunocompromised patients. It is essential for clinicians to be aware of this complication to initiate appropriate management in a timely manner and prevent complications such as postherpetic neuralgia.