Test for the snowdrop dilution of the SLC45A2 gene, described in Gypsy Cob horses with a cremello appearance that did not carry the classic cream, pearl or spotting variants. Complementary to, not a substitute for, clinical examination.

Applicable breed: Traditional Gypsy Cob (United Kingdom). Frequencies: limited data; described in one family.

• Marked dilution phenotype, similar to cremello (light cream coat).\n• Without needing to carry cream, pearl or spotting alleles.\n• Light skin and absence of the patches of other patterns.

In 2020 Bisbee and colleagues described, in a Gypsy Cob mare phenotypically cremello and negative for the known dilutions and patterns, a variant in SLC45A2 that they named snowdrop (C^sno).

• Interpret together with cream, pearl and sunshine, as they share the gene.\n• Avoid combining SLC45A2 dilution alleles unless there is a defined objective.\n• Do not assume classic cremello without genotyping the SLC45A2 variants.\n• A negative result does not rule out other causes of dilution.

It provides a molecular explanation for 'false double dilutes'. It is advisable to genotype the four described alleles of SLC45A2 (cream, pearl, sunshine and snowdrop) before concluding.

1. Bisbee 2020, Identification of a novel missense variant in SLC45A2 associated with dilute snowdrop phenotype in Gypsy horses (PMID 31961951); OMIA:001344-9796.