*'''Aa''' - A blood group found in horses of clinical significance. Aa positive foals born to an Aa negative mare could suffer from equine neonatal isoerythrolysis.
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*'''Aa''' - A blood group found in horses of clinical significance. Aa positive foals born to an Aa negative mare could suffer from equine neonatal isoerythrolysis
*'''Acantholysis''' - loss of cohesion between cells of living epidermis, especially stratum spinosum
*'''Acantholysis''' - loss of cohesion between cells of living epidermis, especially stratum spinosum
*'''Acanthosis''' - hyperplasia of stratum spinosum
*'''Acanthosis''' - hyperplasia of stratum spinosum