Approach to the Problem
Hyperpigmented lesions are caused by localized melanin deposition in the skin. Congenital lesions may occur over time as sun exposure increases the amount of melanin contained within these lesions. Patients and their families frequently have concerns about the cosmetic effects of these lesions and the malignant potential of certain lesions. A careful history and examination, following the lesions closely over time, and referring to appropriate specialists when needed, can reassure patients and families and often result in the correct diagnosis and management.
Key Points in the History
• A history of pustules present at birth that evolve into hyperpigmented macules is characteristic of neonatal pustular melanosis.
• Café au lait spots grow proportionally to overall body growth in the first few years of life and then stabilize.
• Café au lait spots may be a benign familial trait. A family history of neurofibromatosis and the presence of more than six café au lait spots should raise suspicion for neurofibromatosis.
• Only 1% of pigmented lesions at birth are congenital melanocytic nevi.
• Freckles are common in light-skinned, red-haired individuals, and are an autosomal-dominant, inherited trait.
• Freckles are induced by sunlight and are more prominent in the summer and fade in the winter.
• Acanthosis nigricans is associated with overweight/obesity, polycystic ovary syndrome, and the metabolic syndrome—particularly in association with diabetes mellitus with insulin resistance.
• Dermal melanocytosis (previously called Mongolian spots) fades after the first 5 to 10 years of life.
Key Points in the Physical Examination
• A combination of small 1 to 3 mm hyperpigmented macules and pustules is seen in neonatal pustular melanosis.
• A complaint of a “dirty neck” is frequently associated with the physical finding of acanthosis nigricans, which is commonly seen in association with an elevated body mass index.
• Acanthosis nigricans has a velvety quality and may have papillomatous growths within the area of hyperpigmentation.
• Weight loss can result in improvement or resolution of acanthosis nigricans.
• Dermal melanocytosis is often seen in the sacral or gluteal areas, but may also be present elsewhere on the body, including the dorsum of the hand, the upper back, and the shoulders.
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