Characterized by fine, scaly, round or oval patches of skin, pityriasis alba is a fairly common condition that occurs mostly in children between the ages of 6 and 16 and is self-limiting. The scaly patches, which are at first reddish, usually resolve with the affected areas becoming transiently hypo-pigmented (i.e., of a lighter coloration than they previously were). These hypopigmentations usually take some time before they go away and the skin returns to its normal color. Pityriasis alba most frequently manifests on the face and neck and as well as the upper arms and upper torso.
There is a variable duration of the rash lesions associated with pityriasis alba. They may last from several months to well over a year and most patients do not seek medical advice until the rash resolves and becomes hypopigmented with well-circumscribed borders and furfuraceous (bran-like) scales. Pityriasis alba is more easily visualized in individuals with a darker complexion and in lighter skinned people it may be become more noticeable when they are tanned. Although it is a benign, chronic inflammatory dermatosis, there is a high frequency of relapses that are characterized by unsuccessful therapy.
While the cause of the condition is unknown, the rash appears to worsen during times when the skin is drier than usual (e.g. during winter). Moreover, the rash tends to be much more flakier under dry skin conditions. Other factors that have been found to contribute to the pathogenesis of pityriasis alba include climatic changes in temperature and humidity and prolonged exposure to excessive sunlight and altitude. In addition to the aforementioned factors, some studies suggest a potential relationship between pityriasis alba and a positive family or personal history of diseases such as atopic eczema, allergic rhinitis, and asthma.
Pityriasis alba can be easily confused with another rash called tinea versicolor or pityriasis versicolor. Although we all have fungus living on our skin, the out of control growth of such fungus and an autoimmune response directed against it results in tinea versicolor. This condition is one of the most common skin diseases seen in tropical and subtropical countries. Pityriasis versicolor can be distinguished from pityriasis alba with the use of potassium hydroxide examination of the skin tissue under the microscope. Fungal elements can be visualized in the case of pityriasis versicolor, but not in those of pityriasis alba.
Another common condition that pityriasis alba may be confused with is vitiligo. Vitiligo causes the skin to lose its color when the color-giving cells of the skin called melanocytes die as a result of mechanisms that are not fully understood. This results in some areas of the skin appearing lighter than others. The condition itself is fairly benign; however, it may lead to psychological issues affecting the individual’s self-esteem. Pityriasis alba can be distinguished from vitiligo by studying the nature of the border of the rashes. In vitiligo, the rash has a very distinct border that sharply demarcates the affected and unaffected skin areas.
As mentioned earlier, pityriasis alba is a benign and self-limiting condition and as such does not require any treatment. Children who are affected by pityriasis alba usually have lesions that are completely resolved by adulthood. Despite the lack of any need for treatment, there are therapies that may aid in speeding up the recovery process. Moisturizing lotions and/or hydrocortisone creams may be used to clear up the rash more quickly, but do not guarantee fast recovery as lesions may still take many months before fully resolving.
Reviewed by Susha Cheriyedath, MSc