Bunny Hopping Syndrome 1 / CMM1 (EFNB3-related) - Weimaraner

What does this test examine?

This genetic test analyses the EFNB3 variant c.643_644dup in the Weimaraner. The disorder is also described as Bunny Hopping Syndrome 1, BHS1, Congenital Mirror Movement Disorder 1, CMM1, congenital mirror movement disorder or EFNB3-related movement disorder.

What does BHS1 / CMM1 mean for the dog?

EFNB3 is involved in the development of nerve pathways that coordinate left and right movement. In affected puppies, this left-right coordination is disrupted. The hind limbs in particular cannot move independently in a normal way, resulting in a characteristic bunny-like hopping gait. The disorder is congenital and severe: puppies can show coordination problems, restricted mobility, falling or strongly reduced independent movement.

This test provides a clear genetic explanation for a striking movement pattern and supports breeding selection in Weimaraners. The name Bunny Hopping describes the recognisable jumping gait, while CMM1 points to the neurological mechanism: unintended mirror movements because the normal separation between left and right movement is not correctly established.

Inheritance and result

BHS1 / CMM1 is inherited as an autosomal recessive trait. A dog with one copy is a carrier and does not develop the disorder from one copy, but can pass the variant on. A dog with two copies develops the disorder. Testing breeding dogs allows breeders to choose combinations in which affected puppies are not expected.

Practical value of this test

• Helps identify carriers before they are used for breeding.
• Prevents carrier x carrier combinations that can produce affected puppies.
• Provides clear information for puppy buyers, breeders and veterinarians when a line or family connection is relevant.
• Supports keeping valuable carriers in breeding by combining them responsibly with clear-tested partners.
• Clarifies the difference between BHS1/CMM1 and other movement or developmental disorders in young dogs.