Diagnosis: Infantile Eczema (Atopic Dermatitis)
The most likely diagnosis is A. infantile eczema (atopic dermatitis), based on the characteristic age-specific distribution pattern of itchy, weepy, crusty lesions affecting the face (cheeks), scalp, trunk, and extensor surfaces in a 1-year-old child. 1
Clinical Reasoning
Age-Specific Distribution Pattern Confirms Infantile AD
In infancy, atopic dermatitis characteristically starts on the cheeks and extends over time to the neck, trunk, and extensor surfaces of extremities, with notable sparing of the diaper area. 1
The Taiwan Academy of Pediatric Allergy, Asthma and Immunology diagnostic criteria require pruritus with symmetrical and age-specific distribution patterns, which this patient demonstrates. 1
Facial involvement (cheeks or forehead) is typical for children younger than 4 years, distinguishing infant eczema from the flexural pattern seen in older children. 2
Scalp involvement in a "balaclava-like pattern" extending to the forehead, ears, and neck is characteristic of early infantile AD. 3
Lesion Characteristics Match Acute AD
The weepy, crusty, and cracked appearance represents acute atopic dermatitis lesions, which present as erythema, exudation, papules, and vesiculopapules. 1
Acute lesions of AD begin as erythematous papules with serous exudates, and secondary lesions include excoriations and crusted erosions due to scratching. 4, 5
The presence of pruritus (itchiness) is a key diagnostic feature and essential criterion for diagnosis. 1, 2
Why Other Options Are Less Likely
Idiopathic urticaria (Option B) presents with transient wheals that resolve within 24 hours, not persistent weepy, crusty lesions. 4
Drug-induced allergy (Option C) would require a temporal relationship with medication exposure and typically presents with different morphology. 4
Early childhood eczema (Option D) is essentially the same as infantile eczema but typically refers to children older than 2 years with flexural involvement rather than extensor surfaces. 1
Critical Red Flags to Assess Immediately
Examine for multiple uniform "punched-out" erosions or vesiculopustular eruptions, which indicate eczema herpeticum requiring immediate systemic acyclovir. 2, 6
Check for extensive crusting, weeping, or honey-colored discharge suggesting secondary Staphylococcus aureus infection requiring antibiotic therapy. 2, 6, 4
Diagnostic Confirmation
The diagnosis is clinical and does not require laboratory testing when three essential criteria are met: (1) pruritus with age-specific distribution, (2) eczematous lesions, and (3) chronic or relapsing course >2 months in infancy. 1
Observable scratching or rubbing behavior confirms pruritus in infants who cannot verbalize symptoms. 2
A family history of atopic conditions (asthma, allergic rhinitis, or eczema) in first-degree relatives supports the diagnosis. 2
Common Diagnostic Pitfalls to Avoid
Do not dismiss facial rashes as simple "baby acne" without evaluating for atopic features such as pruritus, xerosis, and extensor involvement. 2
Do not overlook secondary bacterial or viral infection, as complications are common in infant eczema and necessitate targeted antimicrobial therapy. 2, 6
Rash in the diaper area of infants is rarely AD; its presence should prompt consideration of alternative diagnoses. 4, 5