A 3-year-old child has eczematous dermatitis on extensor surfaces. His mother has a history of Bronchial asthma. Diagnosis should be –
High-Yield Explanation
In this question:-
The child is 3 years old
History of Asthma in mother
Extensor involvement
First two points suggest the diagnosis of atopic dermatitis (childhood pattern).
About third point (extensor involvement) :-
"Though childhood atopic dermatitis mainly involves flexural parts, less commonly extensor surfaces may also be involved".
Further, you can easily rule out other three options:-
Contact dermatitis
The family history of asthma is not important.
No history of contact to an allergen.
Seborrheic dermatitis
Occurs in adults and less frequently in infants but not in children.
Infantile eczematous dermatitis
Occurs in Infant.