**Question:** More than _____ of body surface is involved in Erythrodermic psoriasis.

**Core Concept:**
Erythrodermic psoriasis is a severe form of psoriasis characterized by widespread, erythematous, scaly rash affecting more than 90% of the body surface area. It is a rare but life-threatening condition that requires immediate medical attention.

**Why the Correct Answer is Right:**
In erythrodermic psoriasis, the skin becomes extremely red and scaly, affecting a large portion of the body surface area. This severity is why the correct answer is "more than 90%." Erythrodermic psoriasis is considered a medical emergency due to potential complications, such as electrolyte imbalances, dehydration, and infections.

**Why Each Wrong Option is Incorrect:**
Option A (more than 5% of body surface area) is incorrect because erythrodermic psoriasis involves a significantly larger area, typically exceeding 90% of the body surface area.

Option B (less than 90% of body surface area) is incorrect because erythrodermic psoriasis generally involves more than 90% of the body surface area, as explained above.

Option C (less than 25% of body surface area) is incorrect because erythrodermic psoriasis typically involves a much larger area than just 25%.

Option D (25-90% of body surface area) is incorrect because erythrodermic psoriasis involves more than 90% of the body surface area, as mentioned above.

**Clinical Pearl:**
Erythrodermic psoriasis is a critical condition that demands immediate medical attention due to potential life-threatening complications. Understanding the severity of the condition is essential for appropriate diagnosis and management.