Skeletal dwarfism (achondroplasia) caused by variants in ACAN (aggrecan), a cartilage matrix protein. It presents with markedly reduced height, abnormal proportions and osteoarticular abnormalities; homozygotes have a more severe phenotype. The test is complementary to the clinical and radiographic examination.

Caballo miniatura, Shetland, Cuarto de Milla and Warmblood. Frequencies: limited data.

- Disproportionate dwarfism (short limbs)
- Angular limb deformities
- Joint abnormalities and lameness
- More severe phenotype in homozygosity

The dossier records five variants D1–D5 in ACAN and warns of localisation errors in the literature for D4. No author or year is stated.

- Genotype breeding animals for variants D1–D5
- Avoid matings that generate homozygosity
- Select breeding animals of normal height and proportions

Differential diagnosis with B4GALT7 dwarfism, skeletal atavism and other dysplasias. Complementary: joint radiography.

1. OMIA:001271 Enanismo (ACAN) del caballo