The clinical image provided shows multiple, well-demarcated, milky-white patches on the dorsum of the hand and fingers. What is the most likely diagnosis?

Explanation

## Image Findings * Multiple **depigmented patches** on the dorsal aspect of the hand and fingers. * Patches are **milky-white** in color, indicating complete loss of pigmentation. * Lesions are **irregular in shape** with **sharp, well-demarcated borders**. * The surrounding skin appears normally pigmented. ## Diagnosis **Key Point:** The presence of well-demarcated, milky-white patches of complete depigmentation is pathognomonic for **Vitiligo**. The image clearly demonstrates the classic features of **vitiligo**, an acquired chronic pigmentary disorder characterized by the selective destruction of **melanocytes**. The lesions are typically **asymptomatic**, presenting as distinct, **milky-white macules or patches** with sharply defined borders, often symmetrically distributed. The complete absence of pigment, as seen in the image, differentiates it from other hypopigmentary conditions. Common sites include the dorsum of hands, face, and body folds. ## Differential Diagnosis | Feature | Correct Dx: Vitiligo | Alt 1: Tinea versicolor | Alt 2: Pityriasis alba | Alt 3: Post-inflammatory hypopigmentation | | :-------------------------- | :------------------------------------------------- | :---------------------------------------------------- | :------------------------------------------------------ | :-------------------------------------------------------- | | **Color** | **Milky-white (complete depigmentation)** | Hypopigmented (fawn/pink/white, incomplete) | Faintly hypopigmented, subtle | Variable, often incomplete, follows prior lesion | | **Borders** | **Sharp, well-demarcated** | Irregular, often ill-defined | Ill-defined, subtle | Variable, often follows shape of previous inflammation | | **Texture/Surface** | Smooth | Fine scale (often visible on scraping), may be pruritic | Fine scale, dry, slightly erythematous initially | Smooth, may have residual scarring or textural changes | | **Wood's Lamp Examination** | **Accentuated bright white** | Yellow-green fluorescence (sometimes) | No specific fluorescence | No specific fluorescence | | **Etiology** | Autoimmune destruction of melanocytes | *Malassezia* yeast infection | Mild eczema/dermatitis, often in children/adolescents | Healing process after inflammation, trauma, or infection | ## Clinical Relevance **Clinical Pearl:** Vitiligo can be associated with other autoimmune conditions, most commonly **thyroid disease** (Hashimoto's thyroiditis, Graves' disease), but also pernicious anemia, Addison's disease, and type 1 diabetes mellitus. Screening for these conditions may be warranted. ## High-Yield for NEET PG **High-Yield:** Vitiligo is an **autoimmune disorder** leading to the destruction of melanocytes. **Key Point:** The **Koebner phenomenon** (lesions appearing at sites of trauma) can be observed in vitiligo. ## Common Traps **Warning:** Do not confuse the complete depigmentation of vitiligo with the incomplete hypopigmentation seen in conditions like **tinea versicolor** or **pityriasis alba**. Tinea versicolor often has subtle scaling and may fluoresce under Wood's lamp, while pityriasis alba presents with less distinct borders and is often seen in children with atopic diathesis. ## Reference [cite:Robbins Basic Pathology, 10th Edition, Chapter 25: Skin, Hair, and Nails; Harrison's Principles of Internal Medicine, 20th Edition, Chapter 65: Disorders of Pigmentation]