The cause of atypical myopathy has been discovered - what should we do now?

This review chronicles the events that led to the discovery of the cause of atypical myopathy (AM). Knowledge of the pathophysiological process of AM has guided the search for the aetiological agent towards toxins that reproduce the biochemical defect identified, whereas epidemiological enquiries indicated that the toxin we were looking for was linked to the environment, especially trees. A toxin named hypoglycin A was known to induce the human Jamaican vomiting sickness, which presents a similar pathophysiology to AM. This human disease results from the ingestion of a tropical fruit borne by a tree of the same family as Acer pseudoplatanus, the latter being consistently found within the vicinity of AM cases. Owing to a collaboration between Europe and the US, it was demonstrated that the toxic metabolite of hypoglycin A was present in the blood of AM cases and further studies confirmed the presence of hypoglycin A in the seeds of Acer pseudoplatanus. An incidence of outbreaks of AM may easily be linked to falling fruits in the autumn, but up to recently, the cause of spring outbreaks was unknown. This review answers the question, "How do horses get poisoned in the spring?" and raises the possible role of humidity or other trees in the disease induction. Recent findings that might be of importance to prevent and/or cure AM are also summarised. The paper concludes with the necessity to continue the recording of cases to help horses' owners prevent AM.