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Pityriasis alba (pityriasis streptogenes, pityriasis corporis, pityriasis faciei) occurs in all races but is more apparent on darker skin in the summertime, when the affected areas fail to tan. This is primarily an affliction of young children and occurs equally in boys and girls. In a study of piteriasis alba.
Pityriasis alba appears as superficial, pale pink to light brown macules with irregular, poorly circumscribed margins. It is round-to-oval in shape and can have slightly elevated borders. Initially the lesion starts as a subtle erythema, which progresses over weeks to produce the characteristic off-white macule with powdery scale. Two to three macules are usually present, with a diameter of 5 to 30 mm. They tend to be located in the midforehead, malar ridge, perioral, and periorbital areas. Involvement of the neck, trunk, back, limbs, and scrotum occurs less commonly. Patients are usually asymptomatic but can experience mild pruritus or burning. The macules persist for 6 months to several years with most patients reporting the disappearance of lesions with increasing age. In a 10-year survey of 67 patients at the Mayo Clinic.
Pityriasis alba is an eczematous dermatosis with hypomelanosis secondary to postinflammatory changes and the UV screening properties of the hyperkeratotic and parakeratotic epidermis. Drying agents such as sunlight, wind, or soap trigger the disorder on the predisposed fragile skin of children, similar to the effect of these agents in children with atopic dermatitis. Wells et al in 1960 concurred that the cause of pityriasis alba was a localized inflammatory reaction.
Clinical presentation and history are usually sufficient for diagnosis. Pityriasis alba lacks the complete depigmentation and distinct margins present in vitiligo. It is also important to rule out dermatophytic infections with scrapings and microscopic examination.
Simple lubrication of the area with petrolatum and emollients is In some patients, however, the lesions Mild topical corticosteroids with and without phototherapy, benzoic and salicylic acid in Aquaphor, and 2% crude coal tar in petrolatum.