| Abbreviations | Meaning |
 | MPS | Hereditary Giant Platelet Syndrome |
 | MPS | Meconium Plug Syndrome |
 | MPS | Montreal Platelet Syndrome |
 | MPS | Myofascial Pain Syndrome |
 | MRK | Mayer-Rokitansky-Küster [syndrome] |
 | MRKH | Mayer-Rokitansky-Kuster-Hauser Syndrome |
 | MRKH | Mayer-Rokitansky-Küster-Hauser [syndrome] |
 | MRS | Magnetic Resonance Spectroscopy; Mania Rating Scale; Medical Receiving Station; Medical Record Summary; Melkersson-Rosenthal Syndrome |
 | MRSD | Mental Retardation-skeletal Dysplasia [syndrome] |
 | MRXA | X-linked Mental Retardation-aphasia Syndrome |
 | MRXS | Mental Retardation, X-linked, Syndrome |
 | MS | Maffuci Syndrome |
 | MS | Marfan Syndrome |
 | MS | Marie-Strümpell [syndrome] |
 | MS | Meckel Syndrome |
 | MS | Menkes Syndrome |
 | MSC-LSMS | Mid-systolic Click-late Systolic Murmur Syndrome |
 | MSEL | Materials Science And Engineering Laboratory; Myasthenic Syndrome Of Eaton-Lambert |
 | MSLS | Marinesco-Sjögren-like Syndrome |
 | MSP | Münchausen Syndrome By Proxy |
 | MSS | Marinesco-Sjögren Syndrome |
 | MSS | Marshall-Smith Syndrome |
 | MST | Myeloproliferative Syndrome, Transient |
 | MSW | Mallory-Weiss Syndrome |
 | MTB | Methylthymol Blue; Michelin Tire Baby [syndrome]; Mycobacterium Tuberculosis |
 | MTS | Mohr-Tranebjaerg Syndrome |
 | MTSS | Medial Tibial Stress Syndrome |
 | MUS | Mouse Urologic Syndrome; Muscinol |
 | MVP-SC | Mitral Valve Prolapse-systolic Click [syndrome] |
 | MVPS | Medicare Volume Performance Standards; Mitral Valve Prolapse Syndrome |
 | MW | Mallory-Weiss [syndrome] |
 | MW | Minot-von Willebrand [syndrome] |
 | MWS | Marden-Walker Syndrome; Moersch-Woltman Syndrome |
 | NADR | National Acquired Immunodeficiency Syndrome [AIDS] Demonstration Research; Noradrenalin |
 | NAME | National Association Of Medical Examiners; Nevi, Atrial Myxoma, Myxoid Neurofibroma, Ephelides [syndrome] |
 | NARES | Nonallergic Rhinitis-eosinophilia Syndrome |
 | NARP | Neuropathy-ataxia-retinitis Pigmentosa [syndrome] |
 | NAS | Neonatal Airleak Syndrome |
 | NAS | Neuroallergic Syndrome |
 | NB | Neuro-Behcet [syndrome] |
 | NBCCS | Nevoid Basal Cell Carcinoma Syndrome |
 | NBS | Nevoid Basal Cell Carcinoma Syndrome |
 | NBS | Nijmegen Breakage Syndrome |
 | NBS | Nystagmus Blockage Syndrome |
 | NCS | Neurocutaneous Syndrome |
 | NCS | Nystagmus Compensation Syndrome |
 | NES | Night Eating Syndrome; Not Elsewhere Specified |
 | NFDR | Neurofaciodigitorenal [syndrome] |
 | NFJ | Naegeli-Franceschetti-Jadassohn [syndrome] |
 | NFNS, NF-NS | Neurofibromatosis-Noonan Syndrome |