A 3 year old child has eczematous dermatitis on extensor surfaces. His mother has a history of Bronchial asthma. Diagnosis should be
First, the core concept here is atopic dermatitis. Eczematous dermatitis in a child, especially with a family history of atopic diseases like asthma, points towards atopic dermatitis. The extensor surfaces are a key location—usually, in atopic dermatitis, infants have flexural involvement, but in older children, it can shift to extensor surfaces. Wait, but some sources say that in early childhood, it's more common on the extensor surfaces. Maybe I should check that again.
Wait, the mother has bronchial asthma. Atopic diseases cluster in families, so this is a classic case of the atopic triad: eczema, asthma, and allergic rhinitis. So the diagnosis here is atopic dermatitis. The options might include other types of eczema, like contact dermatitis or seborrheic dermatitis. Contact dermatitis is usually more acute and localized, but in a child with a family history, it's less likely. Seborrheic dermatitis would present in seborrheic areas like the scalp or face, not extensor surfaces.
So the correct answer should be atopic dermatitis. Let me make sure the options would include that. If the options are A. Atopic dermatitis, B. Contact dermatitis, C. Seborrheic dermatitis, D. Psoriasis, then the answer is A. The clinical pearl here is that atopic dermatitis is part of the atopic triad and has a strong familial component. The extensor involvement in a child with a family history of asthma is key. I should structure the explanation accordingly, making sure to cover why the other options are wrong and the core concept.
**Core Concept**
Atopic dermatitis (eczema) is a chronic inflammatory skin condition with strong genetic predisposition, often part of the "atopic triad" (eczema, asthma, allergic rhinitis). It typically presents with pruritic, eczematous lesions on flexural surfaces in older children but may involve extensor surfaces in early infancy. Family history of atopic diseases is a key risk factor.
**Why the Correct Answer is Right**
The child’s eczematous rash on extensor surfaces and the mother’s history of bronchial asthma strongly suggest **atopic dermatitis**. This condition is mediated by a combination of impaired skin barrier function (e.g., filaggrin gene mutations) and Th2-driven immune hyperactivity. The familial link to asthma supports a diagnosis of atopy, as all atopic conditions share common immunopathogenic mechanisms (IgE-mediated hypersensitivity, Th2 cytokine dominance).
**Why Each Wrong Option is Incorrect**
**Option B: Contact dermatitis** – This is an allergic or irritant reaction to exogenous substances, typically localized to exposed skin areas (e.g., hands, face), not symmetric extensor surfaces.
**Option C: Seborrheic dermatitis** – Presents with greasy, scaly plaques in seborrheic areas