- Mountain
- Mouse, joint (see also Loose, body, joint) 718.1
- Mouth - see condition
- Movable
- Movement
- Moya Moya disease 437.5
- Mozart's ear 744.29
- MRSA (methicillin-resistant staphylococcus aureus) V09.0
- Mu-chain disease 273.2
- Mucha's disease (acute parapsoriasis varioliformis) 696.2
- Mucha-Haberman syndrome (acute parapsoriasis varioliformis) 696.2
- Mucinosis (cutaneous) (papular) 701.8
- Mucocele
- Mucocutaneous lymph node syndrome (acute) (febrile) (infantile) 446.1
- Mucoenteritis 564.9
- Mucolipidosis I, II, III 272.7
- Mucopolysaccharidosis (types 1-6) 277.5
- Mucormycosis (lung) 117.7
- Mucosa associated lymphoid tissue (MALT) 200.3
- Mucositis - see also Inflammation, by site 528.00
- Mucous - see also condition
- Mucoviscidosis 277.00