All of the following are true about erythema infectiosum EXCEPT?
**Core Concept**
Erythema infectiosum, also known as fifth disease, is a common childhood illness caused by parvovirus B19. It is characterized by a distinctive rash, fever, and mild systemic symptoms. The condition is highly contagious and typically affects children.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of erythema infectiosum. Parvovirus B19 primarily targets erythroid progenitor cells in the bone marrow, leading to a temporary anemia. This is particularly concerning in individuals with pre-existing anemia or sickle cell disease, as it can trigger a severe anemia crisis. The rash is thought to be an immune-mediated response to the virus.
**Why Each Wrong Option is Incorrect**
**Option A:** Erythema infectiosum is indeed more common in children, but it can also affect adults, particularly those with underlying health conditions.
**Option B:** The rash of erythema infectiosum typically starts on the face and spreads to other parts of the body, but it can also be preceded by a low-grade fever and mild systemic symptoms.
**Option C:** Parvovirus B19 is the primary cause of erythema infectiosum, and it is highly contagious, but it can also cause other conditions, such as arthropathy and fetal anemia in pregnant women.
**Clinical Pearl / High-Yield Fact**
A key aspect of erythema infectiosum is its potential to cause a transient aplastic crisis in individuals with pre-existing anemia, particularly those with sickle cell disease. This highlights the importance of recognizing the condition and taking appropriate measures to prevent complications.
**Correct Answer:** D.