What are the possible causes and treatments for white spots on a 9-year-old's face?

White Spots on a 9-Year-Old's Face: Differential Diagnosis and Management

The most likely diagnosis is pityriasis alba, a benign hypopigmentation disorder common in children with atopic tendencies, presenting as ill-defined, scaly, hypopigmented patches on the cheeks 1, 2.

Primary Differential Diagnoses

Pityriasis Alba (Most Common)

• Presents as ill-defined, scaly patches of hypomelanosis typically on the cheeks of children with an atopic diathesis 2
• The American Academy of Dermatology recommends low-potency topical corticosteroids (hydrocortisone 1-2.5%) applied 1-2 times daily for 1-2 weeks when inflammatory features are present 1
• For children ages 0-6 years, use only the lowest potency formulations due to increased risk of HPA axis suppression 1
• Tacrolimus 0.1% ointment is recommended as an alternative for facial lesions, particularly suitable for prolonged use without risk of cutaneous atrophy 1
• Never use high-potency or ultra-high-potency corticosteroids on the face in children 1

Vitiligo (Second Most Important to Rule Out)

• Characterized by complete pigment loss with sharply demarcated depigmented macules or patches, favoring periorificial distribution (around mouth, nose, eyes) 3, 2
• Unlike pityriasis alba, vitiligo shows complete depigmentation rather than partial hypopigmentation 2
• The British Journal of Dermatology recommends topical calcineurin inhibitors (tacrolimus 0.1% or pimecrolimus 1%) as first-line treatment for localized vitiligo in children 4
• Thyroid function tests including anti-thyroglobulin antibodies should be performed before starting treatment, given the high prevalence of autoimmune thyroid disease in vitiligo patients 4
• Psychological evaluation of both child and parents is essential, as vitiligo significantly impacts quality of life 4
• Document extent with serial photographs every 2-3 months to monitor treatment response 4

Tinea Versicolor (Pityriasis Versicolor)

• Favors the upper trunk of adolescents rather than face, though facial involvement can occur 2
• Potassium hydroxide (KOH) examination of scale reveals hyphal and yeast forms of Malassezia species 2
• Topical treatments should be first-line in children due to favorable safety profile 5

Nevus Depigmentosus

• A stable, congenital leukoderma present from birth, distinguishing it from acquired conditions 2
• Does not progress or change over time, unlike vitiligo which is acquired and progressive 2

Critical Diagnostic Features to Assess

Examine for these specific characteristics:

• Degree of depigmentation: Partial (pityriasis alba) vs. complete (vitiligo) 2
• Border definition: Ill-defined (pityriasis alba) vs. sharply demarcated (vitiligo) 2
• Scale presence: Fine scale suggests pityriasis alba or tinea versicolor 2
• Distribution pattern: Cheeks (pityriasis alba) vs. periorificial (vitiligo) vs. trunk (tinea versicolor) 2
• Onset timing: Congenital (nevus depigmentosus) vs. acquired (vitiligo, pityriasis alba) 2
• Associated atopy: History of eczema, asthma, or allergic rhinitis suggests pityriasis alba 2

Diagnostic Workup Algorithm

1. Perform Wood's lamp examination: Enhances visualization of hypopigmentation and helps distinguish complete depigmentation (vitiligo) from partial 6
2. KOH preparation if scale present: Rules out tinea versicolor 2
3. If vitiligo suspected, order thyroid function tests including anti-thyroglobulin antibodies 4
4. Document with photographs for monitoring progression or response to treatment 4

Treatment Approach by Diagnosis

For Pityriasis Alba:

• Hydrocortisone 1-2.5% applied 1-2 times daily for 1-2 weeks maximum 1
• Limit treatment duration to 2-4 weeks maximum to prevent adverse effects 1
• Tacrolimus 0.1% ointment for prolonged facial use if needed 1
• Avoid systemic corticosteroids 1
• Avoid topical antibiotics as they are unnecessary and increase resistance risk 1

For Vitiligo:

• Tacrolimus 0.1% or pimecrolimus 1% as first-line (response rate 58% for facial lesions) 4
• Potent topical corticosteroids (clobetasol 0.05% or betamethasone valerate 0.1%) for maximum 2 months if calcineurin inhibitors fail 4
• Narrowband UVB phototherapy for extensive or refractory cases, preferred over PUVA 4
• Psychological interventions and parental counseling should be offered 4
• Never use systemic corticosteroids in children due to unacceptable toxicity 4
• Surgical treatments are not recommended in pediatric patients 4

Common Pitfalls to Avoid

• Do not use potent or ultra-potent corticosteroids on the face in children with pityriasis alba 1
• Do not prolong corticosteroid use beyond 2-4 weeks to prevent skin atrophy 1, 4
• Do not assume all white spots are benign: Always consider vitiligo and its associated autoimmune comorbidities 4, 6
• Do not forget thyroid screening in vitiligo patients: Hashimoto's thyroiditis is the most common association in children 6
• Do not overlook psychological impact: Both vitiligo and visible facial lesions significantly affect quality of life 4