A3-year-old child presents with eczematous dermatitis over the extensor surfaces. His mother has the history of bronchial asthma. What should be the most probable diagnosis?
**Core Concept**
Atopic dermatitis, also known as eczema, is a chronic inflammatory skin condition characterized by dry, scaly, and itchy skin. It often presents in childhood and is frequently associated with other atopic conditions, including asthma and allergic rhinitis. The condition is strongly linked to a genetic predisposition and an imbalance in the skin's natural barrier function.
**Why the Correct Answer is Right**
The presence of eczematous dermatitis on the extensor surfaces, combined with a family history of bronchial asthma, strongly suggests an atopic predisposition. This is consistent with the concept of "atopy" - a genetic tendency to develop allergic diseases. The child's symptoms are likely the result of an overactive immune response, characterized by the release of pro-inflammatory cytokines and the production of IgE antibodies. This leads to the activation of mast cells, resulting in the release of histamine and other mediators that cause the characteristic skin symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because seborrheic dermatitis typically presents on the scalp, face, or trunk, rather than the extensor surfaces.
**Option B:** This option is incorrect because psoriasis is characterized by well-defined, scaly plaques, which are not typically seen in atopic dermatitis.
**Option C:** This option is incorrect because contact dermatitis is caused by an allergic reaction to a specific substance, which is not supported by the family history of asthma.
**Clinical Pearl / High-Yield Fact**
Atopic dermatitis is often associated with other atopic conditions, including asthma and allergic rhinitis. The presence of one of these conditions should prompt a thorough evaluation for the others.
**Correct Answer:** C.