- Autosensitivity, erythrocyte 287.2
- Autotopagnosia 780.99
- Autotoxemia 799.89
- Autumn - see condition
- Avellis' syndrome 344.89
- Aversion
- Aviators
- Avitaminosis (multiple NEC) (see also Deficiency, vitamin) 269.2
- Avulsion (traumatic) 879.8
- Awaiting organ transplant status V49.83
- Awareness of heart beat 785.1
- Axe grinders' disease 502
- Axenfeld's anomaly or syndrome 743.44
- Axilla, axillary - see also condition
- Axonotmesis - see Injury, nerve, by site
- Ayala's disease 756.89
- Ayerza's disease or syndrome (pulmonary artery sclerosis with pulmonary hypertension) 416.0
- Azoospermia 606.0
- Azorean disease (of the nervous system) 334.8
- Azotemia 790.6
- Aztec ear 744.29
- Azygos lobe, lung (fissure) 748.69
