Albinism

Albinism Basics - Pale & Precise

• Hereditary disorders; ↓ or absent melanin synthesis.
• Types: Oculocutaneous (OCA) & Ocular (OA).
• Key enzyme: Tyrosinase (often deficient/defective in OCA).
• Features: Pale skin, white/light hair, translucent irides, nystagmus, photophobia, ↓visual acuity.
• ↑Risk of sun damage & skin cancers (SCC, BCC).

⭐ OCA1A (tyrosinase-negative) is the most severe form, with complete lifelong absence of melanin pigment formation globally; it is an autosomal recessive condition.

Melanin Mystery - Gene Scene

• Core Defect: Impaired melanin biosynthesis from tyrosine.
• Inheritance: Mostly Autosomal Recessive (AR).
• Key Enzyme: Tyrosinase (melanin catalyst).
  • Pathway: Tyrosine → DOPA → DOPAquinone → Melanin.
• Major Genes & OCA Types:
  • TYR → OCA1 (A/B): Tyrosinase -ve/+ve.
  • OCA2 (P gene) → OCA2.
  • TYRP1 → OCA3 (Rufous).
  • SLC45A2 → OCA4.

⭐ TYR gene mutations in OCA1A cause complete, lifelong absence of melanin.

Albinism Spectrum - Shades of Pale

• Heterogeneous group of inherited disorders of melanin biosynthesis.
• Results in generalized or localized hypopigmentation of hair, skin, and/or eyes.
• Key ocular findings: nystagmus, photophobia, ↓ visual acuity, foveal hypoplasia.
• All Oculocutaneous Albinism (OCA) types are Autosomal Recessive (AR).

Head-to-Toe Signs - Clearly Seen

• Skin: Milky-white/cream-colored, extreme sun sensitivity; ↑ risk skin cancers (SCC, BCC).
• Hair: White/yellow/light brown, may darken with age; remains hypopigmented.
• Eyes:
  • Iris: Translucent (pink/blue), severe photophobia.
  • Nystagmus: Pendular, often horizontal.
  • Strabismus: Common.
  • Foveal hypoplasia: ↓ Visual acuity (often <6/60).
  • Optic nerve misrouting.
  • ↑ Refractive errors (myopia, hyperopia, astigmatism).

⭐ Foveal hypoplasia, an underdeveloped fovea, is a consistent finding and primary cause of reduced visual acuity in albinism.

Spotting & Support - Care Plan

• Diagnosis: Hypopigmentation (skin, hair, eyes).
• Key Ocular Signs: Nystagmus, photophobia, ↓ visual acuity, iris transillumination, foveal hypoplasia.
• Tests: Hair bulb tyrosinase test; genetic testing.
• Care Plan:
  • Sun protection: Sunscreen (SPF >30-50), protective clothing, sunglasses.
  • Regular skin exams: Monitor for SCC, BCC.
  • Ophthalmologic care: Corrective lenses, low-vision aids.
  • Genetic counseling.

⭐ Albinism patients have a significantly increased risk of developing Squamous Cell Carcinoma (SCC), primarily due to chronic UV radiation exposure.

High-Yield Points - ⚡ Biggest Takeaways

• Albinism: autosomal recessive; deficient melanin production.
• OCA1 (Tyrosinase-related): OCA1A (absent enzyme, severe) vs OCA1B (residual activity, milder).
• OCA2 (P gene defect): most common type worldwide, especially in individuals of African descent.
• Key ocular features: nystagmus, photophobia, ↓ visual acuity, foveal hypoplasia, iris transillumination.
• Markedly ↑ risk of skin cancers (SCC, BCC) due to UV sensitivity.
• Hermansky-Pudlak Syndrome: albinism, platelet defect (bleeding diathesis), ceroid lipofuscin storage.
• Chediak-Higashi Syndrome: albinism, immunodeficiency, recurrent pyogenic infections, giant lysosomal granules in leukocytes.