Pityriasis Alba in Emergency Medicine 

Pityriasis alba is a term derived from the words scaly (pityriasis) and white (alba).

Characteristic pityriasis alba is shown in the image below.

Debate exists as to the term extensive pityriasis alba (EPA), which some believe to be a confusing misnomer applied to a pathoetiologically different entity and has the proposed name of "progressive extensive hypomelanosis". EPA is believed to be a primary, acquired hypopigmentation observed in females aged 18-25 years of mixed ethnic origin; it is characterized by hypochromic, nonscaly macules developing on the back and abdomen, increasing in number and progressively coalescing over the whole trunk into larger patches surrounded by smaller well-defined macules. Although the single skin lesions of EPA do not differ substantially from those of pityriasis alba, consistent differences are as follows:^[1]

• A widespread and symmetric involvement of the trunk by numerous, round, nonscaly hypomelanotic patches without a preceding inflammatory phase and chronic in duration (This is as opposed to face predominance in pityriasis alba.)
• Histologic examination shows a decrease of epidermal melanin; spongiosis is absent.
• Ultrastructural studies suggested reduced number of active melanocytes and a decrease in number and size of melanosomes.
• No atopy and no associated pathologies or familial occurrences have been reported.
• The age of occurrence; the sex ratio (female preponderance)
• Widespread lesions of classical pityriasis alba can be observed in atopic dermatitis, but they should not be confused with the disorder described by Zaynoun as EPA.

Some authors believe EPA overlaps with another condition described "progressive and extensive hypomelanosis" in persons of mixed racial background and also reported as "progressive and confluent hypomelanosis of the melanodermic metis" or "creole dyschromia". The alternate name of "progressive extensive hypomelanosis" has been proposed.^[1]

No known cause of pityriasis alba has been reported. Atopy and postinflammatory changes are leading current theories as to the origin of the lesions. Theories of origin include hypopigmentation secondary to pityriacitrin, a substance produced by Malassezia yeasts, that acts as a natural sunscreen.

A large number of patients with pityriasis alba have a history of atopic disease. In addition, atopic patients are more prone to developing pityriasis alba.^[2]

Histology of biopsy studies show features including hyperkeratosis (33.33%), parakeratosis (40%), acanthosis (53.33%), spongiosis (80%), and perivascular infiltrate (100%).^[2] However, these findings are not specific enough to make the diagnosis.

Atrophic sebaceous glands were noted in almost half the cases in one study.^[3]

Anemia has been reported in up to 16% of patients.^[2] This may be a coincidental finding, and the clinical relevance of anemia is not yet known.

Ultrastructure studies note that despite a reduced pigment in lesional skin, there is no difference in melanocytes between lesional and nonlesional skin in the same patient, although this finding is still under debate. Degenerative changes in melanocytes and reduced keratonocyte melanosomes were also noted.^[3] Overall, the defect is believed to be due to decreased melanin.

Frequency

United States

Pityriasis alba is relatively common, occurring in up to 5% of children, but the exact epidemiology has not been described.

Mortality/Morbidity

Pityriasis alba is often an incidental finding on clinical examination and generally a self-limited asymptomatic disease that may resolve without intervention. Mortality is not associated with this condition. Cosmetic appearance may be of concern in extensive disease.

Race

Pityriasis alba does not seem to be more prevalent in any race; however, it is more obvious in dark-skinned individuals.

Sex

No sex predilection has been noted. A slight male predominance has been noted.^[2]

Age

Pityriasis alba is most often noted in those younger than 20 years.