Pediatric Dermatology: Diagnosing by Age, Morphology, and Distribution
Core concepts
Pediatric dermatology rewards pattern recognition anchored to age and morphology. The same papule means different things in a newborn, a toddler, and an adolescent. Build a mental index of conditions that are (a) neonatal and transient, (b) inherited/genetic, (c) inflammatory, and (d) infectious.
Know the benign neonatal eruptions cold: erythema toxicum neonatorum (blotchy erythema with yellow-white pustules on an erythematous base, eosinophil-rich, sparing palms/soles), transient neonatal pustular melanosis (pustules that rupture leaving collarette scale and hyperpigmentation, more common in darkly pigmented infants), milia and miliaria (obstruction at different depths), and seborrheic dermatitis of the scalp. Distinguish these from vesiculobullous and erosive presentations of serious disease such as staphylococcal scalded skin syndrome, herpes simplex neonatorum, and epidermolysis bullosa.
Vascular lesions require a vocabulary: infantile hemangioma (appears after birth, proliferates, involutes), capillary malformation (present at birth, grows with the child, does not involute), and port-wine stain associations. Know when a lesion warrants workup (large segmental hemangioma, midline lesions, multiple lesions).
Atopic dermatitis is the workhorse: age-dependent distribution (face/scalp in infancy, flexures in childhood), pruritus as an essential feature, and the role of barrier dysfunction and secondary infection.
Traps
- Confusing miliaria with erythema toxicum (miliaria follows heat/occlusion and clear vesicles; toxicum is idiopathic pustules with eosinophils).
- Assuming any neonatal pustule is infectious.
- Calling a congenital vascular lesion a hemangioma when it is present and fully formed at birth.
- Missing acanthosis nigricans as a marker of insulin resistance in an obese adolescent.
Rule of thumb
If a lesion is present at birth and grows proportionally with the child, think malformation; if it appears days after birth and grows faster than the child, think proliferation (e.g., infantile hemangioma).