A 7-year-old African American girl was brought to her family physician by her mom, who was worried that she was itching and that her skin was getting darker. The physician knew the girl well as a patient with asthma and allergic rhinitis. In fact the girl performed the allergic salute more than once in the office as she rubbed her itchy nose. Morgan-Dennie lines were seen under her eyes (Figure 207-1A). The mom undressed the girl to show the dark patches of skin around her knees (Figure 207-1B). Atopic dermatitis is common in the popliteal fossae, and this girl clearly demonstrated the atopic triad: atopic dermatitis, asthma, and allergic rhinitis. The darkening of the skin around the knees and also seen on the neck is related to the scratching and rubbing of the skin secondary to the pruritus of atopic dermatitis. The physician explained to the mom and child about the need to more aggressively treat the atopic dermatitis with emollients and topical steroids. No promises were made about the reversibility of the hyperpigmentation, as each patient will respond differently to treatment.
A. Atopic triad in a 7-year-old girl with Dennie-Morgan lines and a nasal crease. B. Postinflammatory hyperpigmentation around the knees in the same girl. (Reproduced with permission from Richard P. Usatine, MD.)
Postinflammatory hyperpigmentation (PIH) is an accumulation of melanin in response to chronic inflammation that usually appears as brown, black, or gray macules or patches in the pattern of an underlying inflammatory condition. PIH can result from any kind of irritant to the skin, but is more common in conditions resulting in chronic irritation and inflammation and is more common in individuals with darker Fitzpatrick skin types IV, V, and VI. It is more severe and longer lasting if the underlying inflammatory condition goes untreated, though most PIH will fade within 6–12 months of treating the underlying inflammatory condition. For the girl in the case above, the PIH may resolve without treatment if her atopic dermatitis clears up, but if the atopic dermatitis persists, then the PIH will continue until the resolution of the underlying condition.
The prevalence of disorders of hyperpigmentation including PIH in the general population has been reported as low as 0.42% in Kuwait to as high as 55.9% in Michigan.1
The prevalence in children in the United States is around 22% based on a sample of hospitalized children in Kentucky.2
PIH is one of the most common types of cutaneous hyperpigmentation, and although there are no good estimates of its prevalence in the children of the United States, studies in Nigeria estimate PIH to represent 49.5% of skin lesions present ...