Congenital ocular disease of the Irish soft-coated wheaten terrier caused by a variant in the RBP4 gene, which encodes retinol-binding protein 4, involved in vitamin A transport during embryonic development. The alteration produces microphthalmia (small eye) with congenital retinal folds and dysplasia. It is an identified genetic cause of ocular malformation in the breed and is inherited in an autosomal recessive manner.

Affected breed: Irish soft-coated wheaten terrier. Phenotype described in specific lines; no reliable carrier frequency figures in large series.

- Bilateral microphthalmia from birth (small eye)\n- Congenital retinal folds and retinal dysplasia/disorganisation\n- Possible associated anterior segment abnormalities\n- Variable visual deficit depending on severity, up to blindness\n- No systemic signs in most cases

Microphthalmia with retinal folds in the Irish soft-coated wheaten terrier was described as a congenital ocular entity of the breed, which prompted its genetic study. The identification of a variant in the RBP4 gene as the molecular cause was published in the 2010s, within the framework of studies on ocular development genes in the dog. The finding enabled the development of a DNA test for screening breeding animals in the breed.

- Test Irish soft-coated wheaten terrier breeding animals with the RBP4 test before the first mating\n- Do not mate two carriers: 25% risk of affected homozygotes in each litter\n- A carrier may be mated to a clear animal; offspring intended for breeding must be tested and clear animals preferentially selected\n- If a litter has puppies with small eyes or retinal folds, confirm by ophthalmology and genetic testing, and do not repeat the parental mating\n- Exclude affected homozygous animals from breeding\n- Communicate the status to the buyer and record the result in the pedigree

The phenotype depends on the mother's genotype (maternal inheritance): a homozygous puppy born to a non-homozygous mother does not express the disease. Confirm with ophthalmology and RBP4 genotyping. There is a commercial conflict of interest in the original study (the authors market the test).

Kaukonen M et al. 2018. Maternal Inheritance of a Recessive RBP4 Defect in Canine Congenital Eye Disease. Cell Rep. PMID: 29847795