Coat dilution in the domestic cat is a recessive trait caused by a one-base deletion in the MLPH gene (melanophilin). Cats homozygous for the dilution allele show lightened colours (blue, bluish grey, lilac, cream, etc.) depending on the base colour. Unlike the dog, in the cat MLPH dilution has not been associated with health problems such as colour dilution alopecia.

Multi-breed variant widely distributed; in some breeds the diluted colour is a breeding standard. No single reliable population frequencies are available for the species as a whole.

- Coat of lightened or diluted colour (blue, bluish grey, lilac, cream or similar)\n- Diluted colouration of the iris and nose in some individuals\n- No systemic or dermatological signs have been described associated with the variant; it is a colour trait, not a disease

The molecular basis of feline dilution was identified in 2006, when Ishida et al. described a homozygous single-base deletion in MLPH that co-segregates with the diluted phenotype. This mutation is found in many breeds and in the common cat, and is routinely used in cat colour genetics.

- Dilution is a colour trait, not a disease: there is no health reason to avoid matings\n- To obtain diluted offspring, two carriers or diluted cats must be mated; diluted x non-diluted matings do not allow the colour to be predicted without genotyping\n- Genotype D/d when working with breeds or lines in which the diluted colour is relevant\n- Do not confuse it with the effect of other pigmentation genes (Extension, Agouti, white)

Feline MLPH dilution is a clean model of a recessive Mendelian trait with no known pathological consequences, unlike the dog, where MLPH dilution predisposes to colour dilution alopecia (CDA). The dilution allele must be interpreted together with the base colour to predict the final phenotype. The DNA test reliably distinguishes D/D, D/d and d/d.

1. Ishida Y et al. 2006. A homozygous single-base deletion in MLPH causes the dilute coat color phenotype in the domestic cat. Genomics. PMID: 16860533
OMIA000031-9685.