Pityriasis Alba

 Pityriasis Alba (PA)

Low grade type of eczema/dermatitis that primarily affects children. Pityriasis (fine scale) and Alba (pale color or hypopigmentation).

Epidemiology/Pathogenesis

Mainly children/adolescents aged 3 to 16 years affecting boys and girls equally.  More prominent and prevalent in dark skin compared to white skin. Usually disappears by adulthood. Cause is unknown but usually coexists with dry skin and atopic dermatitis.  Usually presents following sun exposure which makes the features more prominent.

Clinical Features

-Mostly affects face (especially cheeks and chin), lateral upper arms and thighs

-White, round-to-oval areas varying in size, on average 2-4 cm in diameter. May have well-demarcated edges or poorly defined edges

-Itch is minimal or absent

-4 stages of each area of Pityriasis Alba:

·         Pink plaque with mild scale just palpable to surface

·         Hypopigmented plaque with fine scale

·         Post-inflammatory hypopigmented macule without scale

·         Resolution

Differential Diagnosis

·         Tinea Versicolor: rarely located on face and hypopigmented areas are more numerous and often confluent. Can be differentiated by KOH.

·         Vitiligo: loss of pigment is permanent; the margin between normal and hypopigmented skin is distinct. Does not scale.

Diagnosis

Usually a clinical diagnosis, however can run tests to exclude other disorders of hypopigmentation:

·         Woods light examination: hypopigmentation does not enhance and no fluorescence

·         Skin biopsy: rarely required but may reveal spongiotic dermatitis and reduction in melanin