Test for the pearl allele of the SLC45A2 gene, a recessive dilution that lightens the coat in a manner similar to a double dilute when combined with cream. Complementary to, and not a substitute for, the clinical examination.

Applicable breed: Pura Raza Española, Lusitano, American Paint and Quarter Horse. Frequencies: limited data.

• Coat dilution in homozygosity or combined with cream (cream-pearl).
• Single carriers show no evident changes.
• The cream-pearl phenotype resembles a double dilute.

Pearl was described in 2019 when Sevane and colleagues identified a variant in exon 4 of SLC45A2 as the cause of pearl dilution in Pura Raza Española horses and related breeds.

• Avoid pearl × cream if the cream-pearl phenotype is not desired.
• As it shares the gene with cream, interpret both results together.
• Do not confuse pearl with champagne or with silver.
• A negative result does not rule out other dilutions.

The pearl allele is frequent in Iberian breeds; its combination with cream explains 'false double dilute' phenotypes. Genotyping the SLC45A2 alleles together is advisable.

1. Sevane 2019, Explicit evidence for a missense mutation in exon 4 of SLC45A2 causing the pearl coat dilution (PMID 30968968); OMIA:001344-9796.