Dermatology

Pityriasis Alba

Pityriasis Alba

Are You Confident of the Diagnosis?

What you should be alert for in the history

Pityriasis alba (PA) is an eczematous dermatosis characterized by patchy hypopigmentation. It is usually seen in children, and is most noticeable in those with darkly pigmented skin, although it may occur in all skin types. The history will usually reveal worsening during the summer, as the contrast between normal and lesional skin becomes greater with sun exposure. Lesions are usually asymptomatic, although they can be slightly pruritic.

Characterisitic findings on physical examination

Physical examination reveals multiple, 0.5-5–cm, ill-defined, finely scaling patches that are symmetrically distributed. Lesions are most commonly found on the face (especially the cheeks), but can also be seen on the trunk, upper extremities, or rarely other locations (Figure 1). They may be slightly erythematous early on, then become hypopigmented. Lesions may persist for months to years, with a chronic relapsing course, but eventually resolve spontaneously.

Figure 1.

Pityriasis alba on the cheek.

Extensive pityriasis alba (EPA) is a variant that is more common in adults and has a more generalized and truncal distribution. The individual hypopigmented patches in EPA are identical to those of classic PA, except that they are usually not preceded by erythema and tend to be more persistent. EPA may be clinically indistinguishable from progressive macular hypomelanosis (PMH), which is possibly caused by Propionibacterium acnes. These conditions may be differentiated by Wood’s lamp examination, which reveals red fluorescence of lesional skin in PMH.

Diagnosis confirmation

The differential diagnosis is fairly broad, and includes vitiligo, tinea versicolor, pityriasis lichenoides chronica, sarcoidosis, and mycosis fungoides. Woods lamp examination can help distinguish PA from depigmented patches of vitiligo, and potassium hydroxide (KOH) preparation would show spores and hyphae in tinea versicolor. A punch biopsy may be useful in excluding the other entities in the differential.

Who is at Risk for Developing this Disease?

Pityriasis alba primarily affects children from 3 to 12 years old, and almost all patients are younger than 16. It is strongly associated with atopy, with a prevalence in the general population of 1%, but up to 32% in atopic individuals. Xerosis also appears to be a risk factor, and frequent bathing and hot water temperatures may exacerbate this. There is also a higher incidence in children with poorer socioeconomic backgrounds.

Other proposed contributing factors include environmental factors such as temperature variations, air humidity, altitude, and excessive sun exposure. Both genders appear to be equally affected in classic PA, although some studies have shown a male preponderance. In contrast, EPA preferentially affects females.

What is the Cause of the Disease?

Etiology

Pathophysiology

While the hypopigmentation seen in pityriasis alba is usually categorized as postinflammatory, the actual pathogenesis is unclear. The number of melanocytes is reduced, as is the number of melanosomes within both melanocytes and keratinocytes. There is normal melanin synthesis and melanosome transfer.

Systemic Implications and Complications

The most significant association of PA is with an atopic diathesis. A detailed personal and family history should be obtained, including questions about asthma, allergic rhinitis, and atopic dermatitis.

Although PA does not have any systemic implications, it is essential to rule out other entities in the differential diagnosis that do, such as sarcoidosis and mycosis fungoides. A biopsy may help in differentiating these conditions.

Treatment Options

Treatment options are summarized in Table I.

Table I.

Treatment options for pityriasis alba
Medical Treatment Physical Modalities
Topical corticosteroids Phototherapy (PUVA)
Tacrolimus 0.1% ointment  
Pimecrolimus 1% cream  
Topical tretinoin  

Optimal Therapeutic Approach for this Disease

Topical corticosteroids are usually considered to be first-line treatment for PA. Given that the most common location is on the face of children, only low-potency steroids, such as hydrocortisone 2.5% (cream, ointment or lotion twice daily) or desonide (0.05% cream, ointment or lotion twice daily) should be used in these cases. For patients with truncal involvement, higher-potency steroids may be considered.

Immunomodulators such as tacrolimus (0.03% in children younger than 15 years or 0.1% in those older than 15 years, twice daily) or or pimecrolimus 1% cream have been reported to be effective, as has topical tretinoin, although this may be too irritating in some cases.

Phototherapy with psoralens plus ultravolet A (PUVA) may be beneficial in extensive cases.

Patient Management

Pityriasis alba usually has a chronic and relapsing course, with months to years before spontaneous resolution. Response to treatment is variable, and it can take weeks to months for noticeable improvement with any of the treatment modalities. The patient should make a follow-up appointment in 2-3 months to assess the efficacy of the treatment. If no improvement is noticed, consideration should be given to changing therapies. Maintenance therapy consists mainly of emollients and sunscreen.

Unusual Clinical Scenarios to Consider in Patient Management

For atypical presentations, other entities that may cause hypopigmentation should be considered (see differential diagnosis above), with a special emphasis on ruling out either sarcoidosis or cutaneous T cell lymphoma (mycosis fungoides).

What is the Evidence?

DiLernia, V, Ricci, C. "Atopic and idiopathic extensive pityriasis alba". Pediatr Dematol. vol. 24. 2007. pp. 578-9.

(A description of presentations of EPA in patients with and without atopic predisposition.)

In, S, Yi, S, Kang, H, Lee, E, Sohn, S, Kim, Y. "Clinical and histopathological characteristics of pityriasis alba". Clin Exp Dermatol. vol. 34. 2008. pp. 591-7.

(A clinicopathological correlation of findings in classic PA.)

Fujita, W, McCormick, C, Parneix-Spake, A. "An exploratory study to evaluate the efficacy of pimecrolimus cream 1% for the treatment of pityriasis alba". Int J Dermatol. vol. 46. 2007. pp. 700-5.

(A randomized study confirming the therapeutic benefit of pimecrolimus for PA.)

Sandhu, K, Handa, S, Kanwar, A. "Extensive pityriasis alba in a child with atopic dermatitis". Pediatr Dermatol. vol. 21. 2004. pp. 275-6.

(Case report of EPA in the setting of atopic dermatitis.)

Sarifakioglu, E. "Extensive pityriasis alba in a nonatopic child". Pediatr Dermatol. vol. 24. 2007. pp. 199-200.

(Case report of EPA in a child with no history or findings of atopy.)

Weber, M, de Avila, L, Albaneze, R, de Oliveira, O, Sudhaus, B, Cestari, T. "Pityriasis alba: a study of pathogenic factors". J Eur Acad Dermatol Venereol. vol. 16. 2002. pp. 463-8.

(Retrospective analysis of possible risk factors for the development of PA.)

DiLernia, V, Ricci, C. "Progressive and extensive hypomelanosis and extensive pityriasis alba: same disease, different names". J Eur Acad Dermatol Venereol. vol. 19. 2005. pp. 370-2.

(Discussion of similarities and differences between EPA and progressive macular hypomelanosis.)

Rigopoulos, D, Gregoriou, S, Charissi, C, Kontochristopoulo, G, Kalogeromitros, D, Georgala, S. "Tacrolimus ointment 0.1% in pityriasis alba: an open-label, randomized, placebo-controlled study". Br J Dermatol. vol. 155. 2006. pp. 152-5.

(A randomized study confirming the efficacy of tacrolimus for PA.)
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