**Core Concept:** Eczematous dermatitis is a skin condition characterized by inflammation and dryness, often affecting the extensor surfaces of the limbs. In children, eczematous dermatitis may be associated with atopic dermatitis and genetic predisposition. Atopic dermatitis is a subtype of eczematous dermatitis that is often triggered by environmental factors, such as allergens, and is commonly seen in patients with a family history of atopy (asthma, hay fever, and allergic rhinitis) and other atopic conditions.

**Why the Correct Answer is Right:** In this case, the child has eczematous dermatitis on extensor surfaces, which is suggestive of atopic dermatitis. The mother's history of asthma further strengthens the diagnosis, as asthma is a manifestation of the atopic diathesis. Eczematous dermatitis is more likely to occur in patients with a family history of atopy, contributing to the diagnosis of atopic dermatitis in this child.

**Why Each Wrong Option is Incorrect:**

A. Atopic dermatitis can be associated with asthma, making the correct diagnosis not necessarily ruled out. However, this option does not consider the clinical presentation of eczematous dermatitis on extensor surfaces.

B. While eczematous dermatitis can be seen in patients with urticaria (hives), this option does not address the specific clinical presentation of eczematous dermatitis on extensor surfaces.

C. Although eczematous dermatitis can be associated with psoriasis, this option does not address the clinical presentation of eczematous dermatitis on extensor surfaces and does not consider the mother's history of asthma.

D. Atopic dermatitis can be associated with food allergies, but the correct diagnosis is primarily based on the clinical presentation and does not consider the mother's history of asthma.

**Clinical Pearl:** Atopic dermatitis is often referred to as "eczema" and is a chronic inflammatory skin disorder with a strong genetic component, often affecting individuals with a family history of atopy (asthma, hay fever, and allergic rhinitis). Atopic dermatitis is characterized by dryness, itching, and eczematous changes to the skin, particularly affecting extensor surfaces. The presence of a mother with asthma supports the diagnosis of atopic dermatitis, which usually presents with a family history of atopy and specific clinical features.