Exercise Intolerance and Exercise-Induced Collapse in Dogs

Some young-adult Labrador Retrievers have a congenital, autosomal recessive disorderthat results in exercise intolerance and collapse after intense exercise. A mutation in the gene that encodes the dynamin 1 protein has been associated with exercise intolerance and exercise-induced collapse; however, heterozygous dogs and dogs that lack the mutation can still be affected. A similar syndrome has been reported in Border Collies (1); however, a genetic mutation has not yet been identified in this breed.

Clinical signs in Labrador Retrievers with this developmental myopathy include episodes of limb weakness followed by ataxia and collapse 5–20 minutes after intense exercise. Reflexes, particularly the patellar reflex, might be decreased or absent. Affected dogs are normal in between episodes, and recovery is rapid.

Homozygous dogs may show clinical signs when they are young (median age 12 months), whereas heterozygous dogs or dogs that lack the mutation might be older (median age 23 months).

Diagnosis is by genetic testing. A commercially available genetic test for exercise-induced collapse is available.

There is no treatment for exercise-induced collapse; affected dogs should avoid intense activities.

For other degenerative/developmental myopathies in dogs, see the Overview for this chapter.