Atypical Myopathy is a potentially fatal condition in horses caused primarily by the ingestion of sycamore seeds but possibly also sycamore seedlings and leaves. This is due to a toxin called hypoglycin A which is primarily found in the seeds but can also be present in seedlings and leads to damage to the horse’s postural and respiratory muscles.
Atypical myopathy is usually seen in autumn when the seeds are falling onto pasture and in spring when seedlings are growing. Clinical signs include stiffness, pain, weakness and difficulty breathing. Atypical myopathy is a medical emergency and a vet should be contacted immediately if you have any concerns that your horse may be suffering from the condition.
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