Oculocutaneous albinism
OCA; types 1β7 plus syndromic albinisms β Hermansky-Pudlak (HPS), Chediak-Higashi (CHS), Griscelli, Cross syndromes
Oculocutaneous albinism (OCA) is a heterogeneous group of autosomal recessive disorders of melanin synthesis, with seven non-syndromic OCA types (OCA1β7) plus several syndromic forms (Hermansky-Pudlak, Chediak-Higashi, Griscelli). Affected individuals have variable hypopigmentation of skin, hair and eyes, congenital nystagmus, foveal hypoplasia, photophobia, reduced visual acuity and absent stereoscopic vision. The skin-oncology importance is the dramatically increased lifetime risk of cutaneous squamous cell carcinoma β particularly in patients with darker-skinned heritage living near the equator (sub-Saharan Africa, parts of South America), where the cumulative UV exposure produces multiple aggressive cSCCs from the second decade onwards. UN Human Rights Council and Africa Albinism Network estimate that the median life expectancy of patients with OCA in equatorial Africa, untreated, is <30 years, almost entirely due to skin cancer mortality. Lifelong rigorous photoprotection, surveillance and surgical / systemic management of cSCC are the cornerstones of care; cemiplimab is increasingly used for advanced disease.
Genetics & types
- OCA1 (TYR) β tyrosinase deficiency; absolute (OCA1A) or partial (OCA1B); the most severe phenotype.
- OCA2 (OCA2) β the commonest form globally, especially in sub-Saharan African populations; partial pigmentation; least severe ocular involvement.
- OCA3 (TYRP1) β "rufous" / red-haired albinism; brown-yellow hair; over-represented in southern Africa.
- OCA4 (SLC45A2) β variable; particularly common in Japan and Northern Europe.
- OCA5β7 β rarer; described in specific kindreds.
- Syndromic albinism:
- Hermansky-Pudlak syndrome (HPS) β OCA + bleeding diathesis (platelet Ξ΄-storage pool deficiency) + pulmonary fibrosis (HPS-1, HPS-4) Β± granulomatous colitis. Multiple genes (HPS1β11). Strong founder effect in Puerto Rican populations.
- Chediak-Higashi syndrome (CHS) β OCA + giant lysosomal granules (peripheral blood smear) + immunodeficiency + bleeding diathesis + accelerated lymphoma (HLH-like). LYST gene.
- Griscelli syndromes (GS1β3) β silvery hair + pigmentary clumping + variable immunodeficiency / neurological features.
- Confirm by clinical features plus germline gene-panel testing (OCA / syndromic albinism panel).
Cardinal clinical features
- Cutaneous β generalised hypopigmentation; some pigmentation possible in OCA2 / OCA3 / OCA4; photodamage prominent on chronic UV exposure (solar lentigines, actinic keratoses, BCC, cSCC); melanocytic naevi often hypopigmented.
- Hair β white-blond (OCA1A); pale yellow / blond (OCA1B / OCA2); red-yellow (OCA3 / "rufous"); pale (OCA4).
- Ocular β congenital nystagmus, foveal hypoplasia, iris transillumination, photophobia, severe refractive error, reduced visual acuity, absent stereoscopic vision.
- Other β none in non-syndromic OCA; for syndromic forms see above.
Cancer risk
- Cutaneous squamous cell carcinoma (cSCC) β dramatically increased; multiple, aggressive, multifocal SCCs from the second decade in equatorial populations; the leading cause of mortality.
- Basal cell carcinoma β increased; less commonly the dominant problem.
- Melanoma β paradoxically not markedly increased in OCA1A (no melanin available for melanomagenesis); modestly increased in OCA2 / OCA3 / OCA4 with partial melanin synthesis. Amelanotic melanoma may be missed clinically.
- Syndromic albinism cancer risks:
- HPS β pulmonary fibrosis is the leading cause of mortality, not cancer.
- CHS β accelerated lymphoma-like phase (HLH); bone-marrow failure; allogeneic transplantation in childhood.
Management
- Multidisciplinary care β dermatology, ophthalmology, paediatric care, social support, clinical genetics; lifelong.
- Photoprotection (the single most important intervention):
- Daily broad-spectrum SPF 50+; reapply 2-hourly; long-sleeved sun-protective clothing; broad-brim hat; UV-protective glasses.
- Avoid peak UV hours.
- Vitamin D supplementation.
- Patient and community education β particularly important in resource-poor equatorial settings.
- Skin surveillance:
- Annual / 6-monthly full-skin examination from infancy.
- Lower threshold for biopsy of any new or changing lesion.
- Aggressive treatment of actinic keratoses and field damage.
- Skin cancer treatment:
- Surgical excision is the cornerstone; large or multifocal SCC may require multiple procedures and substantial reconstruction.
- Adjuvant radiotherapy for incomplete margins / nodal disease.
- Cemiplimab (NICE TA802) for advanced / metastatic cSCC unsuitable for surgery / RT β increasingly used in OCA-related advanced cSCC.
- Field treatment with 5-FU, imiquimod, PDT for AKs.
- Ophthalmology β ophthalmology assessment, refractive correction, low-vision aids, support for visual impairment.
- Genetic counselling and cascade testing.
- Advocacy and human rights support β patients with OCA in some African countries face severe stigma and violence; international advocacy through United Nations Independent Expert on the enjoyment of human rights of persons with albinism, Africa Albinism Network.
References
- GrΓΈnskov K et al. Oculocutaneous albinism β review. Orphanet J Rare Dis; 2007.
- Lekalakala PT et al. Skin cancer in oculocutaneous albinism β clinical aspects. J Skin Cancer; 2015.
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