What is Pityriasis Alba?
Pityriasis alba is a common benign skin disorder of childhood characterized by hypopigmented (lighter-colored), finely scaly patches or macules, typically appearing on the face and upper body, and is considered a minor clinical sign associated with atopic dermatitis. 1
Clinical Characteristics
- Appearance: Hypopigmented patches or macules with fine scaling, typically a few centimeters in diameter 2
- Distribution: Predominantly affects the face, neck, and upper body/trunk 2, 3
- Age group: Primarily occurs in children and adolescents 2, 4
- Skin type predilection: More commonly detected and visible in individuals with darker skin phototypes, though can occur in all skin types 2, 4
- Associated symptoms: May be accompanied by pruritus (itching), though not always present 2
Clinical Course and Pathogenesis
- Natural history: Extended, multistage course with spontaneous remissions and recurrences 2
- Evolution: Lesions are often preceded by erythematous (red) changes before hypopigmentation develops 2
- Mechanism: Results from inappropriate melanosis (pigment production) manifesting as hypopigmentation, likely related to poor cutaneous hydration 4
- Exacerbating factors: Sun exposure increases the contrast between normal and affected skin, making lesions more visible 4
Association with Atopic Dermatitis
- Diagnostic significance: Pityriasis alba is listed as an "associated feature" in the diagnostic criteria for atopic dermatitis, though it is too non-specific to be used as a defining criterion 1
- Relationship: Often coexists with atopic dermatitis and is considered one of its milder forms or atypical manifestations 2, 5
- Minor criterion: Recognized as a minor sign in the Hanifin and Rajka diagnostic criteria for atopic dermatitis 1, 5
- Common association: Xerosis (dry skin) is present in virtually all patients with pityriasis alba, linking it to the atopic diathesis 5
Clinical Variants
- Classic type: Typical facial and upper body involvement with fine scaling 2
- Extensive type: Rare variant with more generalized, symmetrical distribution, predominantly on the trunk rather than face, with less scaling and more persistent lesions 3
- Pigmenting type: Uncommon variant 3
Differential Diagnosis Considerations
Pityriasis alba must be differentiated from other hypopigmentation disorders 4:
- Pityriasis versicolor alba (fungal infection)
- Vitiligo (complete depigmentation)
- Nevus depigmentosus (congenital)
- Nevus anemicus (vascular)
Clinical Significance
- Benign nature: Primarily a cosmetic concern with no serious health implications 2, 6
- Self-limited: Tends to resolve spontaneously over time, though this may take months to years 6
- Marker of atopy: Its presence may indicate underlying atopic tendency and should prompt consideration of atopic dermatitis diagnosis 1