- Monoplegia 344.5
- Monorchism, monorchidism 752.89
- Monteggia's fracture (closed) 813.03
- Mood swings
- Moore's syndrome (see also Epilepsy) 345.5
- Mooren's ulcer (cornea) 370.07
- Mooser bodies 081.0
- Mooser-Neill reaction 081.0
- Moral
- Morax-Axenfeld conjunctivitis 372.03
- Morbilli (see also Measles) 055.9
- Morbus
- Morel-Kraepelin disease (see also Schizophrenia) 295.9
- Morel-Moore syndrome (hyperostosis frontalis interna) 733.3
- Morel-Morgagni syndrome (hyperostosis frontalis interna) 733.3
- Morgagni
- Morgagni-Adams-Stokes syndrome (syncope with heart block) 426.9
- Morgagni-Stewart-Morel syndrome (hyperostosis frontalis interna) 733.3
- Moria (see also Psychosis) 298.9
- Morning sickness 643.0
- Moron 317
- Morphea (guttate) (linear) 701.0