Pediatric Dermatology: Age-Specific Patterns and Pitfalls
Neonatal and infant skin
Newborn skin has distinct physiology: a thinner stratum corneum, higher surface-area-to-weight ratio, and immature thermoregulation. This makes topical absorption higher and toxicity risk greater. Know benign neonatal eruptions that require no treatment: erythema toxicum neonatorum (blotchy erythema with eosinophil-rich pustules in the first days), milia (keratin cysts on the nose), and sebaceous hyperplasia. Distinguish these from pustular melanosis and from serious infections.
Atopic dermatitis and its mimics
Pediatric atopic dermatitis has age-dependent distribution: cheeks and extensor surfaces in infants, flexural creases in older children. The trap is treating a superinfected flare (crusting, weeping, honey-colored) with steroids alone; think impetigo or eczema herpeticum when there are punched-out monomorphic erosions. Eczema herpeticum is an emergency requiring antivirals.
Vascular and pigmented lesions
Infantile hemangiomas appear in the first weeks, proliferate, then involute; they are not present at birth. Port-wine stains are present at birth, do not involute, and may associate with Sturge-Weber syndrome when in the V1 distribution. Congenital melanocytic nevi are present at birth and carry melanoma risk proportional to size.
Infections and infestations
Know that tinea capitis in children causes alopecia with broken hairs and requires oral therapy (griseofulvin or terbinafine); topical agents fail. Scabies in infants can present with vesicles and nodules on palms and soles, not just web spaces.
Worked example: A 2-month-old has a bright red, well-demarcated plaque on the cheek that appeared at 3 weeks and is growing. This is an infantile hemangioma. The trap is a port-wine stain, which would be present at birth and non-proliferative.
Rule of thumb: Present at birth = congenital (port-wine stain, congenital nevus). Appears after birth and grows = infantile hemangioma.