Objective: To identify characteristics of exercise-induced collapse in Labrador Retrievers and compare characteristics for dogs with various dynamin 1 gene (DNM1) mutation statuses.
Design: Retrospective cross-sectional study.
Animals: 109 Labrador Retrievers with a history of recurrent exercise-induced collapse, clinically normal behavior and gait between episodes, and no reason for collapse identified via medical evaluation.
Procedures: Data were collected via surveys from owners of dogs that were tested for an autosomal recessive DNM1 mutation causing DNM1-associated exercise-induced collapse (d-EIC). Dogs were identified as having d-EIC (homozygous for the mutation) or not having d-EIC (heterozygous for or without the mutation). Survey data were reviewed by an investigator unaware of the genotypes of dogs, and collapse characteristics were compared between groups.
Results: 74 dogs had d-EIC; 35 dogs did not have d-EIC. Dogs with d-EIC were young (median age, 12 months) at the time of the first collapse episode; collapse in such dogs typically originated in the hind limbs and was characterized by low muscle tone, clinically normal mentation, and rapid recovery. Dogs without d-EIC were older (median age, 23 months) than dogs with d-EIC; such dogs had various characteristics of collapse that were not consistent with a single disease.
Conclusions and clinical relevance: Characteristics of exercised-induced collapse in Labrador Retrievers with various DNM1 genotypes were identified in this study; findings may help distinguish dogs with d-EIC from those with other types of collapse conditions. Characteristics of collapse in Labrador Retrievers that were not homozygous for the DNM1 mutation differed substantially among dogs and may have been attributable to multiple causes.