Answer: A
Pityriasis alba is a common benign skin disorder that presents as hypopigmented skin most noticeable in darker skin types. It presents as whitish or mildly erythematous patches, commonly on the face, though it can appear on the trunk and extremities as well. It is estimated that about 1% of the general population is affected and may be more common after months with more extended sun exposure.
While a specific cause has not been identified, it is thought to represent post-inflammatory hypopigmentation, and is thought by many experts to be more common in atopic individuals; it is considered a minor clinical criterion for atopic dermatitis. The name relates to its appearance at times being scaly (pityriasis) and its whitish coloration (alba) and may represent a non-specific dermatitis.
It occurs predominantly in children and adolescents, and a slight male predominance has been noted. Even though this condition is not seasonal, the lesions become more obvious in the spring and summer because of sun exposure and darkening of the surrounding normal skin.
Dr. Sofía Guelfand
Physical examination reveals multiple round or oval shaped hypopigmented poorly defined macules, patches, or thin plaques. Mild scaling may be present. The number of lesions is variable. The most common presentation is asymptomatic, although some patients report mild pruritus. Two infrequent variants have been reported. Pigmented pityriasis is mostly reported in patients with darker skin in South Africa and the Middle East and presents with hyperpigmented bluish patches surrounded by a hypopigmented ring. Extensive pityriasis alba is another uncommon variant, characterized by widespread symmetrical lesions distributed predominantly on the trunk. Seborrheic dermatitis presents as a mild form of dandruff, often with asymptomatic or mildly itchy scalp with scaling, though involvement of the face can be seen around the eyebrows, glabella, and nasolabial areas.
University of California, San Diego
Dr. Carrie Vuong
Less common conditions in the differential diagnosis include other inflammatory conditions (contact dermatitis, psoriasis), genodermatoses (such as ash-leaf macules of tuberous sclerosis), infectious diseases (leprosy, and tinea corporis or faciei) and nevoid conditions (such as nevus anemicus). Leprosy is tremendously rare in children in the United States and can present as sharply demarcated usually elevated plaques often with diminished sensation. Hypopigmentation secondary to topical medications or skin procedures should also be considered. When encountering chronic, refractory, or extensive cases, an alarm for pityriasis lichenoides chronica and cutaneous lymphoma (hypopigmented mycosis fungoides) might be considered.
University of California, San Diego
Dr. Lawrence F. Eichenfield
Pityriasis alba is a self-limited condition with a good prognosis and expected complete resolution, most commonly within 1 year. Patients and their parents should be educated regarding the benign and self-limited nature of pityriasis alba. Affected areas should be sun-protected to avoid worsening of the cosmetic appearance and prevent sunburn in the hypopigmented areas. The frequent use of emollients is the mainstay of treatment. Some topical treatments may reduce erythema and pruritus and accelerate repigmentation. Low-potency topical steroids, such as 1% hydrocortisone, are an alternative treatment, especially when itchiness is present. Topical calcineurin inhibitors such as 0.1% tacrolimus or 1% pimecrolimus have also been reported to be effective, as well as topical vitamin D derivatives (calcitriol and calcipotriol).
Suggested reading
1. Treat: Abdel-Wahab HM and Ragaie MH. Pityriasis alba: Toward an effective treatment. J Dermatolog Treat. 2022 Jun;33(4):2285-9. doi: 10.1080/09546634.2021.1959014. Epub 2021 Aug 1.
2. PEARLS: Givler DN et al. Pityriasis alba. 2023 Feb 19. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023.
3. Choi SH et al. Pityriasis alba in pediatric patients with skin of color. J Drugs Dermatol. 2023 Apr 1;22(4):417-8. doi: 10.36849/JDD.7221.
4. Gawai SR et al. Association of pityriasis alba with atopic dermatitis: A cross-sectional study. Indian J Dermatol. 2021 Sep-Oct;66(5):567-8. doi: 10.4103/ijd.ijd_936_20.
Dr. Guelfand is a visiting dermatology resident in the division of pediatric and adolescent dermatology, University of California, San Diego. Dr. Vuong is a clinical fellow in the division of pediatric and adolescent dermatology, University of California, San Diego. Dr. Eichenfield is vice chair of the department of dermatology and distinguished professor of dermatology and pediatrics at the University of California, San Diego, and Rady Children’s Hospital, San Diego. No author has any relevant financial disclosures.