- Mesenteric lymphadenitis
- Mesothelioma
- Metabolic disorders
- Metabolic syndrome
- Metachromatic leukodystrophy
- Metatarsalgia
- Microscopic colitis
- Minimally invasive vitrectomy
- Mitochondrial antibodies
- Mitral valve disease
- Mitral valve prolapse
- Mitral valve regurgitation
- Mitral valve stenosis
- Mittelschmerz
- Mixed connective tissue disease
- Moles
- Molybdenum
- Morphea
- Morton’s neuroma
- Mouth cancer
