Understanding Skin Pigmentation: Why Accurate Diagnosis Matters for White Spots

"Dr. Ng, are these white spots on my arm Vitiligo?" This is one of the most common questions asked in our clinic. The appearance of white patches on the skin often triggers anxiety, with many patients assuming they have developed an autoimmune condition. However, our Center Director, Dr. Chau Yee Ng, MD, PhD, emphasizes a crucial fact: "White spots are not always Vitiligo."

Two Stories, Two Different Diagnoses

Dr. Ng shares two clinical cases that highlight the critical importance of accurate diagnosis:

• Case 1: The Misdiagnosed Senior A 60-year-old woman noticed small white dots on her arms. Fearing it was Vitiligo, she underwent long-term immune therapy and phototherapy without success. Upon Dr. Ng's evaluation, she was diagnosed with Idiopathic Guttate Hypomelanosis (IGH)—a benign, age-related pigment loss linked to sun exposure. It required no medication, only sun protection. The correct diagnosis brought her immense relief and ended unnecessary treatment.

• Case 2: The Missed Opportunity Conversely, another patient presented with pale patches that were initially dismissed as Tinea Versicolor (a fungal infection) and treated with antifungals to no avail. Further examination confirmed it was indeed Vitiligo. Because Vitiligo is an immune-mediated disorder, the misdiagnosis delayed proper immune-modulating treatment during the critical early stage.

Not All White Spots Are Similar

To help patients navigate these conditions, Dr. Ng categorizes six common types of hypopigmentation (white spots):

1. Vitiligo: An autoimmune loss of melanocytes. Patches are distinct, chalky white, and may spread. Requires assessment of disease activity and timely treatment.

2. Idiopathic Guttate Hypomelanosis (IGH): Common in older adults. Small, porcelain-white spots on sun-exposed areas. Benign and related to aging/sun damage.

3. Hypopigmented Mycosis Fungoides: A rare form of cutaneous T-cell lymphoma (cancer) that mimics eczema or vitiligo. A skin biopsy is essential for diagnosis.

4. Piebaldism: A genetic condition present at birth. Characterized by a white forelock of hair and stable white patches that do not spread.

5. Pigmentary Mosaicism (Hypomelanosis of Ito): Genetic anomalies resulting in linear or whorled patterns of hypopigmentation, often appearing in childhood.

6. Pityriasis Alba: Common in children/adolescents. Ill-defined pale patches often associated with dry skin or eczema. Responds well to moisturizers.

The Key is Precision

"Treat what needs treating, and let be what is benign." Dr. Ng stresses that correct diagnosis is the foundation of effective medicine. This philosophy inspired her book, "Black Spots and White Spots Have Something to Say" (黑斑白斑有話要說), aiming to clarify these common confusions for the public.

📘 Learn More: Get Dr. Ng's book at Eslite Bookstore: Click here to purchase