Vitamin D-dependent rickets type IA / VDDR1A (CYP27B1-related) - Pug

What does this test analyse?

This DNA test analyses the CYP27B1 c.261C>A variant in the Pug. The condition is known as vitamin D-dependent rickets type IA, VDR1A, VDDR1A, vitamin D-dependent rickets type 1A and is sometimes described in practical test naming as vitamin D-resistant rickets.

What does this condition mean?

The CYP27B1 gene encodes 1α-hydroxylase, an enzyme needed to convert vitamin D into its active form. When this enzyme does not function properly, the body regulates calcium and phosphate less effectively. Young Pugs can therefore develop problems with bone mineralisation, skeletal growth and muscle function.

Affected puppies can show lameness, painful or deformed limbs, poor growth, weakness, lethargy, abnormal limb posture, low calcium levels and signs of rickets. The condition can be severe during growth.

Inheritance and result

This trait is inherited as an autosomal recessive condition. A dog with C/C does not carry the tested variant. A dog with C/A is a carrier. A dog with A/A is genetically affected and develops the tested CYP27B1-related form of vitamin D-dependent rickets type IA.

Practical value of this test

This test is valuable for breeders and owners because carriers can look healthy, while two carriers can produce affected puppies. The result enables targeted breeding selection and helps recognise young dogs with a risk genotype earlier.

• Clearly distinguishes clear, carrier and genetically affected dogs.
• Supports avoiding carrier-to-carrier matings in breeding programmes.
• Adds information for family screening when rickets, growth problems or skeletal abnormalities occur in a line.
• Enables early follow-up for puppies with a genetically affected genotype.
• Improves transparency for puppy buyers by documenting the hereditary status of breeding dogs.

Result in brief

• C/C: the tested CYP27B1 variant was not detected.
• C/A: the dog is a carrier and can pass on the variant.
• A/A: this genotype causes the tested CYP27B1-related VDDR1A.