Osteochondromatosis / multiple osteochondromas (EXT2-related) - American Staffordshire Terrier

What does this test examine?

This genetic test analyses the EXT2 c.924C>A variant in the American Staffordshire Terrier. The condition is known as osteochondromatosis, multiple osteochondromas, hereditary exostoses, cartilaginous exostoses, diaphyseal aclasis and hereditary deforming chondrodysplasia.

EXT2 is involved in normal cartilage and bone development. The tested variant creates a premature stop codon and can disturb normal regulation of bone and cartilage growth.

What does this condition mean?

Osteochondromatosis is a skeletal disorder in which multiple cartilage-capped bony outgrowths may develop during growth. These outgrowths are called osteochondromas or exostoses and may occur on long bones, ribs and vertebrae.

Affected dogs may develop pain, lameness, reduced movement, neurological compression signs, hindlimb weakness or paralysis. Severity depends on the location, size and growth of the bony outgrowths.

Inheritance and result

The trait is inherited as autosomal dominant. One copy of the EXT2 c.924C>A variant is sufficient for a genetically positive result.

What does the result mean?

• Clear (CC): the tested EXT2 variant was not detected.
• Genetically positive (CA): one copy is detected and gives a genetically positive result.
• Genetically positive (AA): two copies are unusual, but mean that the dog is genetically positive for the tested variant.

Practical value of this test

• Shows whether the known EXT2 variant is present in a dog from a relevant line.
• Helps breeders avoid further use of a proven dominant skeletal variant in a breeding line.
• Supports interpretation when young dogs develop bony outgrowths, lameness or neurological compression signs.
• Provides concrete information for mating decisions, family-line investigation and communication with puppy buyers.
• Separates this known EXT2 variant from other causes of bone or cartilage abnormalities.

For breeding policy, the test is especially useful because a dominant variant should not remain unnoticed when selecting breeding animals.