| Disorder | Symbol(s) | OMIM | Location |
| Marfan syndrome, atypical (3) | COL1A2 | 120160 |
7q22.1 |
| Marinesco-Sjogren syndrome, 248800 (3) | SIL1, BAP, MSS | 608005 |
5q31 |
| Maroteaux-Lamy syndrome, several forms, 253200 (3) | ARSB, MPS6 | 611542 |
5q11-q13 |
| Marshall syndrome, 154780 (3) | COL11A1, STL2 | 120280 |
1p21 |
| Martin-Probst deafness-mental retardation syndrome (2) | MPDMRS | 300519 |
Xq11-q21 |
| Martsolf syndrome, 212720 (3) | RAB3GAP2, RAB3GAP150, p150, KIAA0839 | 609275 |
1q41 |
| Mast cell leukemia (3) | KIT, PBT | 164920 |
4q12 |
| Mast syndrome, 248900 (3) | ACP33, MAST, SPG21 | 608181 |
15q21-q22 |
| Mastocytosis with associated hematologic disorder (3) | KIT, PBT | 164920 |
4q12 |
| Maturity-onset diabetes of the young, type IX, 612225 (3) | PAX4, MODY9, KPD | 167413 |
7q32 |
| Maturity-onset diabetes of the young, type VII, 610508 (3) | KLF11, TIEG2, FKLF1, FKLF, MODY7 | 603301 |
2p25 |
| Maturity-onset diabetes of the young, type VIII, 609812 (3) | CEL, BSSL, CELL, MODY8 | 114840 |
9q34.3 |
| May-Hegglin anomaly, 155100 (3) | MYH9, MHA, FTNS, DFNA17 | 160775 |
22q11.2 |
| McArdle disease, 232600 (3) | PYGM | 608455 |
11q13 |
| McCune-Albright syndrome, 174800 (3) | GNAS, GNAS1, GPSA, POH, PHP1B, PHP1A, AHO | 139320 |
20q13.2 |
| McKusick-Kaufman syndrome, 236700 (3) | MKKS, HMCS, KMS, MKS, BBS6 | 604896 |
20p12 |
| McLeod syndrome (3) | XK | 314850 |
Xp21.2-p21.1 |
| McLeod syndrome with neuroacanthosis (3) | XK | 314850 |
Xp21.2-p21.1 |
| Meacham syndrome, 608978 (3) | WT1 | 607102 |
11p13 |
| Meckel syndrome type 4, 611134 (3) | CEP290, KIAA0373, 3H11AG, JBTS5, SLSN6, LCA10, BBS14 | 610142 |
12q21.3 |
