**Core Concept**
Hereditary angioneurotic edema (HAE) is a rare genetic disorder characterized by recurrent episodes of severe angioedema, which is the rapid swelling of the skin and mucous membranes. This condition is caused by a deficiency or dysfunction of C1 esterase inhibitor (C1-INH), a protein that plays a crucial role in regulating the complement system and the contact activation system.

**Why the Correct Answer is Right**
The correct answer is **Berinert**, a human C1 esterase inhibitor concentrate. Berinert works by replacing the deficient C1-INH protein, thereby inhibiting the excessive activation of the complement system and the contact activation system, which leads to the release of histamine and other mediators causing angioedema. This results in rapid relief of symptoms, including swelling, pain, and difficulty breathing.

**Why Each Wrong Option is Incorrect**
**Option A:** FFP (Fresh Frozen Plasma) is not the primary treatment for HAE. Although it contains C1-INH, the amount is usually insufficient to provide therapeutic benefit.
**Option B:** Corticosteroids, such as prednisone, are not effective in treating acute HAE attacks. They may be used to prevent attacks during stress or with other triggers, but not for acute management.
**Option C:** Antihistamines, such as diphenhydramine, are not effective in treating HAE. They may be used to relieve symptoms of urticaria or allergic reactions but not for angioedema.

**Clinical Pearl / High-Yield Fact**
Berinert is administered intravenously and can provide rapid relief of symptoms within 5-10 minutes. It is essential to note that Berinert should only be used during an acute attack and not for long-term prevention of attacks.

**Correct Answer: C. Corticosteroids are not the primary treatment for acute HAE attacks.