Pityriasis alba


Pityriasis alba

Description, Causes and Risk Factors:

Patchy hypopigmentation of the skin resulting from mild dermatitis.

Pityriasis alba is a common condition in Practice mostly occurring in children between the ages of 3 and 16, but can be additionally seen in young adults. It usually appears as dry, fine scaled, pale patches, 0.5 to 6 cm in diameter; however, often the flakiness is not present. The rash is limited to the face in 50% of cases, particularly the mid-forehead, malar ridges, and around the eyes and mouth; nevertheless, involvement of the shoulders, neck, back, and upper chest may predominate in others. It is symmetrical in distribution, but sometimes only marginally. The condition often begins as a pale pink or light brown macule with very indistinct margins, but it often just appears suddenly with decreased pigmentation. Macules vary from 5 to 30 mm or larger.

The condition is so named as 'pityriasis' means scaly and 'alba' is the word for white in Latin. Of note, the patches in pityriasis alba are not totally depigmented as with vitiligo. The hypopigmentation with pityriasis alba is due to both reduced activity of melanocytes as well as fewer and smaller melanosomes; in vitiligo, on the other hand, there is total loss of both melanocytes and melanosomes. Histologically, the condition reveals subacute spongiotic dermatitis with decreased melanin within the epidermis. A differential diagnosis would include vitiligo, psoriatic leukoderma, tinea versicolor, follicular mucinosis, pityriasis lichenoides chronica, sarcoidosis, adult T-cell leukemia/lymphoma, and mycosis fungoides.

There is no specific known cause for this condition; however, studies to elucidate pathogenic factors seem to suggest that there are at least five separate causes for the condition. Photosensitivity plays a role in this entity. A relative vitamin and calcium deficiency from inappropriate food habits in kids seems to be the most plausible explanation, as pityriasis alba invariably occurs in the growing years in children.

The peak incidence of the condition coincides with the age when children begin to do more outdoor activities. Typical location of lesions is in sun-exposed areas. Also prolonged sun exposure of several hours also increases one's chances of developing the condition. Thus, the melanocytes appear to be sensitive to sun in these patients.

Symptoms:

Pityriasis alba is manifested by multiple non-itchy, oval, mildly scaly, flat hypopigmented (white) patches on the face, arms and upper trunk. The lesions become more prominent after sun exposure as surrounding skin darkens. These lesions are often mistaken for fungal infections and treated inappropriately with antifungals.

Diagnosis:

Diagnosis is usually made solely on clinical signs and symptoms. A potassium hydroxide (KOH) examination may be performed to rule out tinea versicolor, tinea faciei, or tinea corporis.A biopsy may be performed but usually will show unimpressive changes under the microscope.Skin biopsy is not usually necessary or particularly helpful in establishing the diagnosis. It may be indicated if the diagnosis of mycosis fungoides (cutaneous T-cell lymphoma) is a significant possibility.

Treatment:

Pityriasis alba doesn't need to be treated. While it goes away on its own, it may take many months to several years to do so. You can use moisturizers or mild steroid creams to help with the dryness or itchiness. Use sun protection so the rash isn't as noticeable. Using a moisturizer in the dry winter months can sometimes prevent it from coming back in summer. If the rash is widespread and not going away, it is preferable to consult Dermatology.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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