| Abbreviation | Definition |
|---|---|
| MODS | Multi Organ Dysfunction Syndrome |
| MRDS | Mentally Retarded Down's Syndrome |
| MRFS | Multiple Risk Factor Syndrome |
| MRKH | Mayer-Rokitansky-Küster-Hauser syndrome |
| MRLS | Mare Reproductive Loss Syndrome |
| MSBP | Münchhausen Syndrome by Proxy |
| MTBS | Michelin tire baby syndrome |
| MWS | Marden Walker Syndrome |
| MWS | Muckle Wells Syndrome |
| MWWS | Missing White Woman Syndrome |
| NAPS | New Anxious Parent Syndrome |
| NBS | Nijmegen breakage syndrome |
| NCAIS | Non Cardiogenic Alveolar Interstitial Syndrome |
| NCSBS | National Center for Shaken Baby Syndrome |
| NCSBS | National Center on Shaken Baby Syndrome |
| NDS | Nasty Dick Syndrome |
| NDSS | National Down Syndrome Society |
| NES | Night Eating Syndrome |
| NGPS | Nestor Guillermo progeria syndrome |
| NHS | Nance Horan Syndrome |