How does the dilute gene cause Colour Dilution Alopecia?

Colour Dilution Alopecia (CDA) is caused by a recessive genetic variant of the melanophilin (MLPH) gene, commonly known as the dilute gene. When a dog inherits two copies of this recessive variant (the homozygous d/d genotype), it alters the normal formation and storage of pigment in the hair.

Specifically, this genetic variation causes a defect in the transport of melanosomes from the cell center to the periphery. This transport failure leads to the clumping of melanin granules within the hair shaft. These abnormal melanin clumps disrupt the pillar structure, making the hair physically weak and unstable. Because the hair structure is compromised, the hair breaks easily, leading to progressive hair loss (alopecia) that defines the condition.