| Abbreviation | Definition |
|---|---|
| MDDS | Mal de Debarquemnet Syndrome |
| MDF | Map-Dot-Fingerprint dystrophy |
| MDLS | Miller Dieker Lissencephaly Syndrome |
| MDSC | Massachusetts Down Syndrome Congress |
| MDSN | Maine Down Syndrome Network |
| MEBS | Muscle Eye Brain Syndrome |
| MECFS | Myalgic Encephalomyelitis/Chronic Fatigue Syndrome |
| MERS | Middle Eastern Respiratory Syndrome |
| MEWDS | Multilple Evanescent White Dot Syndrome |
| MEWDS | Multiple Evanescent White Dot Syndrome |
| MEWDS | Multiple Evasnescent White Dot Syndrome |
| MFS | Miller Fisher Syndrome |
| MGS | Multiple Geek Syndrome |
| MILS | Maternally Inherited Leighs Syndrome |
| MIS | Multisystem Inflammatory Syndrome |
| MISC | Multisystem Inflammatory Syndrome in Children |
| MLS | Musladin Lueke Syndrome |
| MMDS | Multiple mitochondrial dysfunctions syndrome |
| MNS | Melnick Needles syndrome |
| MNS | Motor Neuron Syndrome |