Ocular and periocular surface neoplasia (limbus, third eyelid, eyelids) favoured by UV exposure and depigmentation. The variant in DDB2 (nucleotide excision DNA repair) acts as a risk factor, not a causal one. It presents with an ulcerated mass, blepharospasm, epiphora and keratitis. The genetic test is complementary to the clinical examination and biopsy.

Tiro belga, Connemara, Haflinger, Noric, Rocky Mountain Horse, Warmblood and Welsh Pony. Frequencies: limited data.

- Exophytic or ulcerated ocular or periocular mass
- Blepharospasm, epiphora and photophobia
- Keratitis and possible corneal ulcer
- Higher risk in areas of high UV radiation and in depigmented skin/eyes
- Possible regional lymphadenopathy due to metastasis

The dossier records OMIA:000735 and the variant DDB2 NC_009155.3:g.11726667C>T (c.1013C>T; p.Thr338Met; rs1139682898). No author or year is stated.

- As it is a risk factor and not a cause, do not eliminate breeding animals on genotype alone
- Avoid concentrating lines with a high familial incidence
- Sun protection and regular ocular examination
- Confirm by biopsy before making selection decisions

Differential diagnosis with sarcoid, basal cell carcinoma, melanoma and conjunctival habronemiasis. Complementary: cytology, biopsy and lymph node inspection.

1. OMIA:000735 Carcinoma de células escamosas ocular del caballo