Pityriasis Alba Clinical Presentation

Updated: Apr 03, 2020
  • Author: Sarah Sweeney Pinney, MD, FAAD; Chief Editor: Dirk M Elston, MD  more...
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Presentation

History

Pityriasis alba (PA) is generally asymptomatic but may be mildly pruritic. Patients may describe any of the following three clinical stages:

  1. Papular erythematous lesions

  2. Papular hypochromic lesions

  3. Smooth hypochromic lesions

Pityriasis alba lesions often occur on the face, with the cheek being a particularly common site. [2] Initially, erythema may be conspicuous, and minimal serous crusting of some lesions may occur. However, because the erythema is usually very mild, most parents of young patients do not recall the erythematous stage. Erythema later subsides completely to leave areas of hypopigmentation with or without fine scaling.

Recurrent crops of new lesions may develop at intervals, with the duration of pityriasis alba varying from 1 month to 10 years. Most cases, however, resolve over a period of several months to 1 year.

Associated factors

Patient or family history may include asthma and hay fever. It may also include eczema in the characteristic areas of atopic dermatitis, with pityriasis alba being a nonspecific finding commonly associated with this condition. [25]

The patient may have a prior history of rash or eczema at the sites of hypopigmentation; skin irritation produced by any of a variety of causes may heal with postinflammatory hypopigmentation.

The patient should be asked about prior therapy; potent topical steroids may produce hypopigmentation. Moreover, patients may develop irritant or allergic contact dermatitis from the use of various topical creams, lotions, or medications; when these are discontinued and the area recovers from the contact dermatitis, an area of postinflammatory hypopigmentation may occur.

The clinician should look for seasonal variations in appearance; the scaling areas of hypopigmentation frequently develop during winter but become more apparent following sun exposure during the spring and summer.

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Physical Examination

The correct diagnosis of pityriasis alba (PA) is usually suggested by the age of the patient, fine scaling, hypopigmentation, and the distribution of lesions.

Characteristic lesions

Pityriasis alba is often diagnosed following an incidental finding on clinical examination. The individual lesions are rounded, oval, or irregular plaques that are red, pink, or skin colored and have fine lamellar or branny scaling with indistinct margins. (See the image below.)

Pityriasis alba. Pityriasis alba.

Usually 1-4 cm in diameter, the lesions most commonly number from 4 or 5 to 20 or more. They are visible primarily in contrast to dark skin; increasing sunlight in spring and summer also makes them more apparent.

Affected areas

The lesions appear on the face, upper arms, neck, or shoulders; the legs and trunk are less commonly involved. In approximately one half of all patients, the lesions are limited to the face. [3] The areas around the mouth, chin, and cheeks are the most commonly affected. (See the image below.)

Lesions of pityriasis alba are usually bilateral a Lesions of pityriasis alba are usually bilateral and located on the face, arms, and neck.

In 20% of affected children, the neck, arms, and shoulders are involved in addition to the face. Less commonly, the face is spared and scattered lesions are present on the trunk and limbs.

Variants

Uncommon variants of pityriasis alba are the pigmenting variety and the extensive type. In pigmenting pityriasis alba, the typical lesion has a central zone of bluish hyperpigmentation surrounded by a hypopigmented, slightly scaly halo of variable width. The lesions are usually confined to the face and are often associated with dermatophyte infection. [4] As previously mentioned, this is more commonly found in patients with darker skin from South Africa and the Middle East. [1]

Extensive pityriasis alba is differentiated from the classic form by the widespread and symmetrical involvement of the skin, the absence of a preceding inflammatory phase, a higher female-to-male ratio, and, histologically, the absence of spongiosis. [5] In the extensive variant, lesions are less erythematous, less scaly, more persistent, asymptomatic, and more frequently seen on the trunk and less often on the face. [6]

Important aspects of examination

Examine patients for keratotic lesions on the elbows and knees and for small pits in the nails, which may suggest a diagnosis of psoriasis.

Examine for the following potential signs of atopic dermatitis:

  • Eczema in the popliteal or antecubital fossa

  • Nipple eczema

  • Cheilitis

  • Dennie-Morgan infraorbital fold

  • Anterior neck folds

  • Wool intolerance

  • White dermographism

  • Infra-auricular fissuring

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