Bullous amyloidosis in a horse: first description in veterinary medicine

Background Bullous amyloidosis is a rare disease in humans that has not been described in a veterinary species in the peer‐reviewed literature. The human disease is characterised by haemorrhagic vesicles and bullae on the skin and mucosae, which form due to amyloid deposition. Hypothesis/Objectives To describe the clinical features, laboratory analysis and histopathological features of an unique presentation of bullous disease in a horse. Animals A 17‐year‐old thoroughbred mare presented for weight loss and severe oral cavity ulcers. Methods and materials Investigations involved haematological evaluation, chemistry profiles, gastroscopy and serum protein electrophoresis, and, postmortem, histopathological evaluation, Congo‐red staining and transmission electron microscopy (TEM). Results Haemorrhagic vesicles and bullae occurred on the mucosa of the oral cavity, lips, oesophagus and stomach, and much less the muzzle, face and mucocutaneous areas of the perineum, where scarring was evident. Histopathological evaluation and Congo‐red staining confirmed the presence of amyloid deposits in dermis and submucosa, in association with vesicle and bulla formation, consistent with bullous amyloidosis. TEM confirmed amyloid fibril deposition in the dermis and along the basement membrane zone. Clefts occurred in the superficial dermis and submucosa, which explained haemorrhage and scarring. The presence of a polyclonal gammopathy and the rapid abolishment of Congo‐red staining with performate pretreatment supported serum amyloid A and secondary amyloidosis. Conclusion and Clinical Importance Bullous amyloidosis is a novel disease of the horse and a newly recognised differential for bullous disease, for which the haemorrhagic nature of bullae, scarring and deep secondary ulcers are considered clinical clues to the condition. Résumé Contexte L’amyloïdose bulleuse est une maladie rare chez l’homme qui n’a pas encore été décrite dans une espèce vétérinaire dans la littérature avec comité de lecture. La maladie de l’homme est caractérisée par des vésicules et bulles hémorragiques de la peau et des muqueuses qui se forment après dépôt d’amyloïde. Hypothèses/Objectifs Décrire les données cliniques, les analyses de laboratoires et les critères histopathologiques d’une présentation unique de maladie bulleuse chez un cheval. Sujets Une jument de race de 17 ans présentée pour perte de poids et ulcères sévères de la cavité buccale. Méthodes Les investigations comprenaient une éval