Vitiligo

Definition & Pathogenesis - Patchy Puzzle Pieces

• Definition: Acquired, chronic depigmenting disorder characterized by the selective loss of functional melanocytes from the epidermis and, occasionally, hair follicles.
• Melanocytes: Neural crest-derived cells responsible for melanin production; primarily in skin (epidermal, follicular reserves), but also eye (uvea) and inner ear.
• Key Pathogenetic Theories:
  • Autoimmune: Most accepted; T-cell (CD8+) mediated destruction of melanocytes.
  • Neural: Neurochemical mediators (e.g., neuropeptides) damage melanocytes or inhibit melanin synthesis.
  • Oxidative Stress: Accumulation of Reactive Oxygen Species (ROS) and ↓antioxidant defenses (e.g., catalase) damage melanocytes.
  • Genetic: Polygenic; associations with HLA (e.g., HLA-DRB1*07) and immune-related genes.
  • Melanocytorrhaphy: Defective melanocyte adhesion and chronic detachment leading to transepidermal loss.

⭐ Koebner phenomenon (isomorphic response), the development of new vitiligo lesions at sites of skin trauma, is a common indicator of active disease progression and is seen in about 20-60% of patients.

Clinical Features & Types - Spot the Signs

• Types:
  • Non-segmental (NSV): Most common; often symmetrical.
    • Generalized: Widespread macules.
    • Acrofacial: Lips, distal fingers/toes.
    • Mucosal: Oral/genital mucosa.
    • Universal: Affects >80% of body surface area.
  • Segmental (SV): Unilateral, dermatomal; earlier onset, stable course.
  • Mixed: Features of both NSV and SV.
• Morphology:
  • Chalky/milky white, depigmented macules or patches.
  • Well-demarcated borders.
  • Trichrome vitiligo: Intermediate zone of hypopigmentation between normal and depigmented skin.
  • Koebner phenomenon: Lesions at sites of trauma.
• Common Sites: Extensor surfaces (elbows, knees), periorificial areas (eyes, mouth, nostrils), hands, feet, genitals.
• Associated Autoimmune Conditions: Thyroid disease (Hashimoto’s, Graves’), alopecia areata, pernicious anemia, type 1 diabetes.

⭐ Wood's lamp examination (wavelength 365 nm) accentuates depigmented areas, appearing as bright blue-white fluorescence, especially useful in fair-skinned individuals where contrast is low under normal light.

Diagnosis & DDx - Confirming the Clues

• Clinical Diagnosis: Based on characteristic depigmented macules/patches.
• Wood's Lamp Examination:
  • Accentuation of depigmentation (chalky white fluorescence).
  • Helps identify subclinical/early lesions.
• Skin Biopsy (Rarely needed):
  • Confirms absence of melanocytes.
  • May show marginal lymphocytic infiltrate.
• Differential Diagnosis (DDx):
  • Pityriasis alba
  • Tinea versicolor (KOH: spaghetti & meatballs)
  • Idiopathic guttate hypomelanosis
  • Piebaldism (congenital, stable)
  • Chemical leukoderma
  • Leprosy (sensory loss)

⭐ Wood's lamp is crucial for detecting subtle lesions and assessing true extent, especially in fair-skinned individuals.

Vitiligo Management - Repigmenting Roadmap

Goals: Arrest progression, induce repigmentation.

• Medical Therapies:
  • Topical: Corticosteroids (e.g., clobetasol propionate), calcineurin inhibitors (tacrolimus, pimecrolimus), JAK inhibitors (tofacitinib).
  • Phototherapy: NB-UVB (311-313 nm), PUVA.
  • Systemic: Corticosteroids (oral mini-pulse for active disease), JAK inhibitors.
• Surgical Therapies (for stable vitiligo):
  • Autologous melanocyte transplant (MKTP), punch grafting, suction blister grafting.
• Depigmentation (extensive vitiligo >80% BSA):
  • Monobenzyl ether of hydroquinone (MBEH).
• Always: Sunscreen use.

⭐ For generalized vitiligo, NB-UVB phototherapy (311-313 nm) is a first-line treatment, offering good efficacy and safety.

High‑Yield Points - ⚡ Biggest Takeaways

• Autoimmune destruction of melanocytes causes well-demarcated depigmented patches.
• Koebner phenomenon (new lesions at trauma sites) is frequently observed.
• Wood's lamp examination accentuates lesions, appearing as chalky white fluorescence.
• Strong association with other autoimmune diseases (e.g., thyroiditis, pernicious anemia).
• Segmental vitiligo follows dermatomes; non-segmental is more common and widespread.
• Mainstay treatments include topical corticosteroids, calcineurin inhibitors, and NB-UVB phototherapy.
• Surgical therapies like melanocyte transplantation are for stable, localized disease_