How Is Vitiligo Diagnosed? Tests and Clinical Evaluation
How Is Vitiligo Diagnosed? Tests and Clinical Evaluation
The Diagnostic Process for Vitiligo
Vitiligo is most often diagnosed through a clinical skin examination. Dermatologists rely on visual assessment of the lesions, including their color, shape, and distribution. However, some cases may require supportive tests to rule out other conditions or confirm uncertain findings.
Key Clinical Features Observed During Diagnosis
During a physical exam, dermatologists look for:
- Milky-white depigmented patches
- Well-defined borders
- Symmetrical distribution (face, hands, genitals, elbows, knees)
- Depigmented body or facial hair (leukotrichia)
- Koebner phenomenon (lesions appear at injury sites)
These clues often make the diagnosis possible without invasive testing.
Wood’s Lamp Examination: Ultraviolet Diagnosis
What is a Wood’s Lamp?
A Wood’s lamp emits long-wave UVA light (around 365 nm) and is used in a dark room to detect changes in skin pigmentation.
What Does Vitiligo Look Like Under Wood’s Light?
- Patches glow bright white or bluish-white
- Clear contrast between vitiligo and surrounding skin
- Helps detect early or subclinical lesions not visible in natural light
This tool is especially helpful in light-skinned individuals, where contrast is minimal in daylight.
Skin Biopsy: When Is It Needed?
A skin biopsy is not routinely required but may be done if:
- The diagnosis is unclear
- There’s suspicion of other conditions that resemble vitiligo
- The patient has atypical or mixed lesions
Findings in Vitiligo Biopsy:
- Loss or absence of melanocytes
- Reduced epidermal melanin
- Immune cell infiltration (in some cases)
Since it’s invasive, biopsy is reserved for specific clinical scenarios.
Blood Tests and Autoimmune Screening
Because vitiligo is often associated with other autoimmune conditions, doctors may order blood tests after diagnosis—not to confirm vitiligo, but to screen for coexisting diseases.
Common Lab Tests:
- TSH, Free T3, Free T4 – To detect thyroid disorders
- Anti-TPO, Anti-TG antibodies – For autoimmune thyroid disease
- Vitamin B12 – Often low in vitiligo patients
- Glucose and HbA1c – For diabetes screening
- ANA and ENA panels – If systemic autoimmune disease is suspected
- 25(OH)D (Vitamin D) – Important for immune regulation
Differential Diagnosis: Other Conditions That Mimic Vitiligo
Several skin conditions resemble vitiligo and must be ruled out:
- Pityriasis alba – Light, flaky patches, common in children
- Tinea versicolor – Fungal infection with hypopigmented or hyperpigmented patches
- Chemical leukoderma – Due to exposure to certain chemicals
- Post-inflammatory hypopigmentation – From prior eczema or trauma
- Albinism – Genetic absence of melanin from birth
Wood’s lamp, biopsy, and careful history help distinguish vitiligo from these.
Special Diagnostic Considerations in Children and Light-Skinned Individuals
In light-skinned people, vitiligo may go unnoticed until sun exposure makes it obvious. In children, it’s often confused with pityriasis alba. Wood’s lamp is especially useful in both cases, and pediatric dermatologic evaluation is key.
Step-by-Step Summary of Vitiligo Diagnosis
- Clinical skin examination
- Wood’s lamp test (to assess extent and early lesions)
- Skin biopsy (if needed)
- Blood tests (to screen for related autoimmune diseases)
- Photography and documentation (for monitoring progression)
Most diagnoses are confirmed in steps 1 and 2; the others are used based on the individual case.
Frequently Asked Questions
In most cases, no. An experienced dermatologist can often make a diagnosis based on visual inspection alone.
No. Biopsies are used when the diagnosis is unclear or to rule out similar conditions.
Yes. It’s especially helpful for detecting early or faint vitiligo lesions.
Not directly. They help identify associated autoimmune disorders that often coexist with vitiligo.
In fair-skinned individuals, Wood’s lamp examination is crucial since the contrast between affected and normal skin may be subtle.