A 16-month-old boy is brought to your office because of red, itchy and crusted patches...

This child’s presentation is classic for atopic dermatitis (eczema) : pruritic, erythematous, crusted patches involving the cheeks in infants and the flexural creases in toddlers. Sparing of the groin and axillae is typical. MCCQE objectives emphasize recognizing age-specific distribution and identifying risk factors. The strongest contributor is a family history of atopy (e.g., asthma, allergic rhinitis, eczema), reflecting a genetic predisposition involving impaired skin barrier function and immune dysregulation (often associated with filaggrin mutations).

Vaccination (e.g., MMR) does not cause eczema. Oral amoxicillin may trigger a transient rash but would not produce chronic pruritic flexural dermatitis. Early introduction of cereals is not an established cause of atopic dermatitis. Varicella-zoster infection produces a vesicular rash in various stages, not chronic flexural eczema.

Thus, a family history of atopic reactions is the most important contributing factor to this child’s condition.