The correct answer is postinflammatory hypopigmentation (choice “c”), in this case secondary to eczema in a classic antecubital location. Leprosy (choice “a”) is more common than one might imagine, but it does not appear overnight and does not involve overt inflammation. Vitiligo (choice “b”) does not appear suddenly and rarely involves the type of inflammation seen in this case. Lichen sclerosis et atrophicus (choice “d”) is an inflammatory condition that presents with hypopigmentation and epidermal atrophy; however, it is gradual in onset and would not exhibit papulosquamous inflammation.
The more color in the skin, the more the loss of that color stands out. Patients and families with darker skin are often understandably upset by the contrast. Providers need a differential for pigment loss, including the items mentioned—some of which have the potential to be dreadfully serious.
Two relevant facts stand out in this case: the rapidity of onset and the history of eczema, in which secondary pigment loss can occur. As mentioned, it is especially obvious in those with darker skin. Fortunately, once the eczema calms down, the hypopigmentation resolves and normal color returns.
Paradoxically, it’s not at all unusual to see postinflammatory hyperpigmentation, especially in those with skin of types IV and V (eg, African-Americans, some Hispanics, and those of Indian ancestry). Eczema is a common cause, but the inflammation can be from almost any source, including trauma, burns, or even acne.
Had this patient’s diagnosis not been obvious, a biopsy might have been indicated due to the serious nature of some of the items in the differential. Vitiligo, for example, can be very disfiguring, especially on a dark-skinned individual. It tends to become widespread and permanent, unless it’s caught and treated early on. Other conditions involving hypopigmentation include sarcoidosis, lupus, and morphea.
All of these conditions are unusual, if not rare, compared with atopic dermatitis (AD), which this patient has. AD is so common that almost 20% of newborns develop it. Eczema is one of the more typical manifestations, along with dry, sensitive skin, seasonal allergies, and reactive airway disease. Corroboration of the diagnosis is usually easily accomplished by taking a family history.
Fortunately, this patient’s hypopigmentation will resolve quickly with treatment of her eczema, using a low-strength steroid cream (eg, hydrocortisone 2.5% cream or ointment). But a good portion of the “treatment” of AD is done by educating the family about the nature of the condition, as well as providing reassurance about the absence of the more serious items in the differential.