Abstract :
[en] Atypical myopathy (AM), also called “atypical myoglobinuria”, is a frequently and rapidly fatal myopathy of unknown origin occurring sporadically in grazing horses. As opposed to the exertional rhabdomyolysis syndrome (ERS), clinical signs of AM are not induced by exercise. The condition has been reported in several European countries including Belgium, France, Germany and Great Britain. Clinical signs of AM are characterised by muscular weakness, stiffness, recumbency, sweating and when urine is observed, myoglobinuria. These signs are characteristic but not pathognomonic of the disease; the differential diagnosis of sudden weakness, severe myopathy and/or unexpected death includes several neurogenic and myopathic disorders. The main pathologies that share clinical similarities with AM include the acute form of grass sickness (GS), acute piroplasmosis, botulism, ERS, the hyperkalemic periodic paresis (HPP), nutritional myopathy (NM; i.e. vitamin E and/or selenium deficiency), plants or drugs (i.e. ionophores intoxication) intoxication, tetanus and postanaesthesia myopathy. This report aims at reviewing key facts in history, clinical signs, clinical examination and laboratory findings that contribute towards the diagnosis of AM and/or invalidate the diagnosis of other pathologies.
