Background
Pityriasis alba is a nonspecific skin disorder of unknown etiology that causes erythematous scaly patches. These resolve and leave areas of hypopigmentation that slowly repigment to normal. Pityriasis alba commonly occurs in children and is considered a self-limited dermatosis.
Pathophysiology
Pityriasis alba has been regarded as a manifestation of atopic dermatitis[1, 2] but is also known to occur in nonatopic individuals. Pityriacitrin, a substance produced by Malassezia yeasts, acts as a natural sunscreen, but much of the hypopigmentation results from a failure of melanin transfer from melanocytes to keratinocytes.[3]
Epidemiology
Frequency
The frequency of pityriasis alba both in the United States and internationally is unknown.
International
A large study in a tropical region in schoolchildren showed that the prevalence of pityriasis alba was 9.9%. Another study in Nepal showed that the prevalence of pityriasis alba within a wide range of dermatoses was 5.2%.[4]
Mortality/Morbidity
Pityriasis alba is not associated with mortality. Pityriasis alba is usually a self-limited, asymptomatic disease.
Race
Pityriasis alba can affect persons of any race, but it may be more prominent and cosmetically more troublesome in dark-skinned patients.[5]
Sex
Both sexes are equally susceptible to pityriasis alba, but it is thought that males are affected more frequently.[6]
Age
Pityriasis alba occurs predominantly in children aged 3-16 years.[5] but can occur in adults.[7]
History
Lesions in pityriasis alba are commonly asymptomatic, although some patients report mild pruritus or a burning sensation.
Lesions tend to worsen in the summer with increased sun exposure.
Erythema is usually mild and may initially be conspicuous. Minimal serous crusting may even occur at a few points on the surface of some of the pityriasis alba plaques. Erythema later subsides completely to leave areas of hypopigmentation with or without fine scaling.
At the stage when a physician commonly observes pityriasis alba lesions, they show only persistent fine scaling and depigmentation. This commonly induces the patient to seek advice.
Pityriasis alba may be conspicuous in heavily pigmented skin. In lighter skins, pityriasis alba may become conspicuous after sun tanning. Pityriasis alba is considered a skin disorder of late summer because reports describe that excessive and unprotected sun exposure are strongly related in the development of pityriasis alba.[6]
Pityriasis alba is associated with atopic diathesis. Inquire about a patient and family history of eczema, asthma, and/or hayfever.[7]
The course of pityriasis alba is extremely variable. Most cases persist for several months, and some still show hypopigmentation for a year or more after all scaling subsides. Hypopigmentation may persist for years but eventually resolves spontaneously.
Recurrent crops of new lesions may develop at intervals.
The average duration of the common facial form in childhood is a year or more.
Widespread cases overlap with a condition termed progressive and extensive hypomelanosis.[8] Progressive and extensive hypomelanosis occurs mainly in women from 18-25 years, with progressive development of round, pale coalescent macules mainly on the back that are unresponsive to therapy but spontaneously regress within 3-4 years.[9]
Physical
The individual pityriasis alba lesion is a rounded, oval, or irregular plaque that is red, pink, or skin colored and has fine lamellar or branny scaling with indistinct margins. Several patches are usually observed.
In children, pityriasis alba lesions are often confined to the face and are most common around the mouth, chin, and cheeks (see the image below). Legs and trunk are less commonly involved.
View Image | Pityriasis alba. |
In 20% of affected children, the neck, arms, and face are involved. Less commonly, the face is spared and scattered pityriasis alba lesions are observed on the trunk and limbs.
Pityriasis alba lesions usually range from 0.5-2 cm in diameter but may be larger, especially on the trunk.
Two uncommon variants exist, a pigmenting variety and an extensive type. In pigmenting pityriasis alba, the typical lesion is a central zone of bluish hyperpigmentation surrounded by a hypopigmented, slightly scaly halo of variable width, usually confined to the face and often associated with dermatophyte infection.[10] Extensive pityriasis alba is differentiated from the classic form by the widespread and symmetrical involvement of the skin, no preceding inflammatory phase, a higher female-to-male ratio, and, histologically, the absence of spongiosis.[11] In the extensive variant, lesions are less erythematous and less scaly, more persistent, asymptomatic, and more frequently seen on the trunk and less on the face.[1]
Causes
The cause is unknown. The condition has been regarded as a manifestation of atopic dermatitis or other mild forms of eczema.
Reported contributory factors related to the development of pityriasis alba are excessive and unprotected sun exposure, poor hygienic habits, and environmental influences such as temperature, humidity, and altitude.[6]
Histologic Findings
Histologic changes are unimpressive. Acanthosis and mild spongiosis are observed, with moderate hyperkeratosis and patchy parakeratosis. A decrease in the number of melanocytes has been reported.[13] Follicular plugging, spongiosis, and sebaceous gland atrophy may be observed.[14] On electron microscopy, reduced numbers of active melanocytes and a decrease in number and size of melanosomes is observed in affected skin.[15]
Medical Care
Pityriasis alba resolves spontaneously and may not require treatment. Treatment may include a simple emollient cream. For chronic lesions on the trunk, a mild tar paste may be helpful.
Topical 1% hydrocortisone preparations may be helpful if mild inflammation is present.[16] Topical 0.1% tacrolimus ointment may be indicated only after other treatment options have failed.[7] Pimecrolimus 0.1% cream has been reported to be effective.[17]
Consultations
A dermatologist may be consulted for cosmetic camouflage.
Diet
No dietary recommendations are currently proposed.
Activity
No specific activity limitations or exercises are recommended. Photoprotection may be considered. Also see Sunscreens and Photoprotection.
Medication Summary
Response to treatment for pityriasis alba often is disappointing.
Aqueous cream (Curel, Cetaphil, Nivea, Lubriderm)
Clinical Context:
Oil in water emulsion that spreads easily and helps retain moisture in the skin.
Class Summary
A variety of lotions, creams, and ointments that contain hydrocarbons, oil, waxes, and long-chain fatty acids aid in retaining moisture in the skin especially if applied immediately after bathing. A bland emollient may be used to reduce the scaling.
Hydrocortisone topical (Cortaid, Dermacort)
Clinical Context:
1% or 2.5% hydrocortisone cream or ointment. Adrenocorticosteroid derivative suitable for application to skin or external mucous membranes. Has mineralocorticoid and glucocorticoid effects resulting in anti-inflammatory activity.
Class Summary
Reducing inflammation helps reduce symptoms and helps resolve lesions.
Tacrolimus (Protopic)
Clinical Context:
Mechanism of action in atopic dermatitis not known. Reduces itching and inflammation by suppressing the release of cytokines from T cells. Also inhibits transcription for genes that encode IL-3, IL-4, IL-5, GM-CSF, and TNF-alpha, all of which are involved in early stages of T-cell activation. Additionally, may inhibit release of preformed mediators from skin mast cells and basophils and down-regulate expression of FCeRI on Langerhans cells. Can be used in patients as young as 2 y. Drugs of this class are more expensive than topical corticosteroids. Available as ointment in concentrations of 0.03 and 0.1%. Indicated only after other treatment options have failed.
Further Inpatient Care
Inpatient care is not generally required for pityriasis alba.
Further Outpatient Care
Regular follow-up is not required for pityriasis alba.
Transfer
Patients requiring cosmetic camouflage may require transfer to another specialist if the dermatologist or primary care physician teams cannot provide this service.
Deterrence/Prevention
Prevention is not possible because the etiology of pityriasis alba is unknown.
Prognosis
The prognosis is good because pityriasis alba almost always resolves spontaneously.
Author
Bassam Zeina, MD, PhD, Consulting Staff, Department of Dermatology, Milton Keynes Hospital, UK
Disclosure: Nothing to disclose.
Coauthor(s)
Nicole Sakka, MBBS, Foundation Year 2, Royal Liverpool and Broadgreen University Hospital, Liverpool, UK
Disclosure: Nothing to disclose.
Sohail Mansoor, MBBS, MSc, Dermatologist and Lead Physician in Dermatologic Surgery, Department of Dermatology, Barnet Hospital, UK
Disclosure: Nothing to disclose.
Specialty Editors
Mark G Lebwohl, MD, Chairman, Department of Dermatology, Mount Sinai School of Medicine
Disclosure: Amgen/Pfizer Honoraria Consulting; Centocor/Janssen Honoraria Consulting; DermiPsor Honoraria Consulting; GlaxoSmithKline Honoraria Consulting; HelixBioMedix Honoraria Consulting; Novartis Honoraria Consulting; Ranbaxy Lectures; Can-Fite Biopharma Honoraria Consulting; DermaGenoma Honoraria Consulting; Biosynexus Honoraria Consulting
David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Chair, Department of Dermatology, Director, Dermatology Residency Training Program, Scott and White Clinic, Northside Clinic
Disclosure: Nothing to disclose.
Christen M Mowad, MD, Associate Professor, Department of Dermatology, Geisinger Medical Center
Disclosure: Nothing to disclose.
Catherine M Quirk, MD, Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania
Disclosure: Nothing to disclose.
Chief Editor
Dirk M Elston, MD, Director, Ackerman Academy of Dermatopathology, New York
Disclosure: Nothing to disclose.
Additional Contributors
The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author, Mohsin Ali, MBBS, FRCP, MRCP, to the development and writing of this article.
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