Epidemiology

Peak incidence: 10–30 years

Etiology

Autoimmune destruction of epidermal melanocytes.
Peak onset: Age 10–30 yrs; equal prevalence across sexes and ethnicities (cosmetically more evident in darker skin types).
Strong association with other autoimmune diseases:
- Autoimmune thyroid disease (Hashimoto thyroiditis/Graves dz — most common association; ~20–30% of pts). c
- Type 1 Diabetes Mellitus (T1DM).
- Alopecia areata.
- Pernicious anemia (atrophic gastritis).
- Primary adrenal insufficiency (Addison disease).
Family history present in ~30% of affected individuals.

Irregular, well-demarcated, depigmented (white) macules or patches
Unilateral or bilateral distribution, with stable or slowly progressive lesions
Leukotrichia: depigmented hair; an indicator of poor prognosis
Coexisting autoimmune diseases (∼ 20% of patients)
- Most common: Hashimoto thyroiditis, Graves disease
- Other disorders: type 1 diabetes, psoriasis, inflammatory bowel disease, alopecia areata, pernicious anemia, Addison disease

Initial / Best Step: Clinical diagnosis based on history, pattern recognition, and physical examination.
Diagnostic Modalities:
- Wood’s lamp examination: Highlights lesions with a bright, chalky-white/blue fluorescence (sharpens contrast against normal surrounding skin; useful in fair-skinned individuals).
- Key Labs: Screening for associated autoimmune endocrinopathies:
  - Serum TSH (most important screening test; check anti-TPO if abnormal). c
  - Fasting blood glucose or HbA1c.
  - Complete blood count (CBC) to screen for pernicious anemia.
- Skin Biopsy (Rarely indicated):
  - Performed only if diagnosis is ambiguous.
  - Histology: Total absence of melanocytes in the basal layer (confirmed via Fontana-Masson or Melan-A staining) and loss of epidermal melanin pigment.
Differential diagnostics: see Catecholamine Synthesis > Albinism

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