A 7-year-old African American girl was brought to her pediatrician by her mom who was worried that she was itching and that her skin was getting darker. The pediatrician 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 168-1A). The mom undressed the girl to show the dark patches of skin around her knees (Figure 168-1B). 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 pediatrician 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. (Used 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 grey macules or patches in the pattern of an underlying inflammatory condition. Postinflammatory hyperpigmentation 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 to 12 months of treating the underlying inflammatory condition. For the girl in the preceding case, the PIH may resolve without treatment after 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 post-inflammatory hyperpigmentation in the general population ranges from 0.42 percent in Kuwait to 55.9 percent in a sample population from Michigan.1
The prevalence in children in the US is around 22 percent based on a sample of hospitalized children in Kentucky.2
Postinflammatory hyperpigmentation (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 US, studies in Nigeria estimate PIH to represent 49.5 percent of skin lesions present in hospitalized children.3 In studies of adults, ...