Diseases of Hypopigmentation / Depigmentation
- Hypopigmentation: lighter color
- Depigmentation: no color
| Condition | Mechanism | Presentation | Key Finding |
|---|
| Vitiligo | Autoimmune -> Absent melanocytes | DEpigmented (milk-white) patches | Autoimmune dz association |
| Oculocutaneous Albinism (OCA) | Genetic defect -> Non-fxn melanocytes | Diffuse hypopigmentation (skin/hair/eyes) | Nystagmus, ↓ visual acuity |
| Phenylketonuria (PKU) | Enzyme defect -> ↓ Melanin synthesis | Diffuse hypopigmentation (fair skin/hair) | Intellectual disability, musty odor |
| Post-inflammatory Hypopigmentation | Inflammation -> ↓ Melanin transfer | HYPOpigmented patches, follows prior rash | Hx of preceding dermatosis |
| Waardenburg Syndrome | Neural crest defect -> Absent melanocytes | White forelock (poliosis), heterochromia iridis | Congenital sensorineural deafness, dystopia canthorum |
| Chédiak-Higashi Syndrome | LYST gene mut -> Microtubule dysfunction | Partial albinism, metallic silver hair | Giant cytoplasmic granules in neutrophils, recurrent infections |
Diseases of Hyperpigmentation
| Condition | Mechanism | Presentation | Key Finding |
|---|
| Melanoma | Malignant proliferation of melanocytes | Asymmetric, irregular border, variable color, >6 mm | Breslow depth is key prognostic factor |
| Melasma | ↑ Melanin production (normal cell #) | Symmetric hyperpigmented patches on face | Linked to pregnancy, OCPs |
| Nevus (Mole) | Benign proliferation of melanocytes | Symmetrical, uniform color, sharp border, <6 mm | Histology: Nests of nevus cells |
| Solar Lentigo | Benign hyperplasia of melanocytes | Brown macules on sun-exposed areas (hands, face) | “Age spots”; do not fade in winter |
| Ephelis (Freckle) | ↑ Melanin production (normal cell #) | Small macules on sun-exposed areas | Fades in winter, darkens in summer |