| Diagnosis | Omim Number | Sample Count |
| MACHADO-JOSEPH DISEASE; MJD | 109150 | 2 |
| MACROGLOBULINEMIA, WALDENSTROM; WM | 153600 | 1 |
| MACROGLOSSIA | 153630 | 1 |
| MACULAR DYSTROPHY, CORNEAL, 1; MCDC1 | 217800 | 1 |
| MACULAR DYSTROPHY, RETINAL, 1, NORTH CAROLINA TYPE; MCDR1 | 136550 | 2 |
| MAJOR AFFECTIVE DISORDER - 125480 OR 309200 | 125480 | 141 |
| MAJOR AFFECTIVE DISORDER - 125480 OR 309200 | 309200 | 141 |
| MAJOR AFFECTIVE DISORDER; OLD ORDER AMISH - 125480 OR 309200 | 125480 | 532 |
| MAJOR AFFECTIVE DISORDER; OLD ORDER AMISH - 125480 OR 309200 | 309200 | 532 |
| MALIGNANT HYPERTHERMIA SUSCEPTIBILITY 1; MHS1 | 145600 | 1 |
| MANDIBULOACRAL DYSPLASIA WITH TYPE A LIPODYSTROPHY; MADA | 248370 | 1 |
| MANNOSIDOSIS, ALPHA B, LYSOSOMAL | 248500 | 7 |
| MANNOSIDOSIS, BETA A, LYSOSOMAL; MANSB | 248510 | 7 |
| MAPLE SYRUP URINE DISEASE (MSUD), TYPE IA | 248600 | 18 |
| MAPLE SYRUP URINE DISEASE (MSUD), TYPE II | 248600 | 3 |
| MARFAN SYNDROME; MFS | 154700 | 68 |
| MARSHALL SYNDROME | 154780 | 6 |
| MASA SYNDROME | 303350 | 1 |
| MATURITY ONSET DIABETES OF THE YOUNG, TYPE II; MODY2 | 125851 | 1 |
| MATURITY-ONSET DIABETES OF THE YOUNG, TYPE I; MODY1 | 125850 | 174 |
| MECKEL SYNDROME; MKS | 249000 | 4 |
| MEDITERRANEAN FEVER, FAMILIAL; MEFV | 249100 | 3 |
| MELANOMA, CUTANEOUS MALIGNANT, 2; CMM2 | 155601 | 4 |
| MENKES SYNDROME | 309400 | 25 |
| MENTAL RETARDATION, AUTOSOMAL DOMINANT 40; MRD40
| | 36 |
| MENTAL RETARDATION, AUTOSOMAL DOMINANT 5; MRD5 | | 4 |
| MENTAL RETARDATION, AUTOSOMAL DOMINANT 52; MRD52
| | 3 |
| MENTAL RETARDATION, AUTOSOMAL RECESSIVE 34; MRT34 | | 5 |
| MENTAL RETARDATION, X-LINKED 102; MRX102 | | 8 |
| MENTAL RETARDATION, X-LINKED 106; MRX106 | | 1 |
| MENTAL RETARDATION, X-LINKED NONSPECIFIC, TYPE 1; MRX1 | 309530 | 2 |
| METACHROMATIC LEUKODYSTROPHY | 250100 | 17 |
| METAPHYSEAL DYSPLASIA, ANETODERMA, AND OPTIC ATROPHY | 250450 | 2 |
| METHIONINE ADENOSYLTRANSFERASE DEFICIENCY | 250850 | 1 |
| METHYLMALONIC ACIDURIA AND HOMOCYSTINURIA, cblC TYPE | 277400 | 2 |
| METHYLMALONICACIDURIA DUE TO METHYLMALONIC COA MUTASE DEFICIENCY | 251000 | 6 |
| METHYLMALONICACIDURIA, VITAMIN B12-RESPONSIVE, DUE TO DEFECT IN SYNTHESIS OF ADENOSYLCOBALAMIN--CBL A | 251100 | 5 |
| METHYLMALONICACIDURIA, VITAMIN B12-RESPONSIVE, DUE TO DEFECT IN SYNTHESIS OF ADENOSYLCOBALAMIN--CBL B | 251110 | 1 |
| MEVALONIC ACIDURIA; MEVA | | 2 |
| MICROCEPHALY WITH CHORIORETINOPATHY | 251270 | 4 |
| MIGRAINE, FAMILIAL HEMIPLEGIC 1, WITH ATAXIA | 141500 | 1 |
| MILLER-DIEKER LISSENCEPHALY SYNDROME; MDLS | 247200 | 6 |
| MITOCHONDRIAL DNA DEPLETION SYNDROME 12 (CARDIOMYOPATHIC TYPE); MTDPS12 | | 1 |
| MITOCHONDRIAL DNA DEPLETION SYNDROME 4A (ALPERS TYPE); MTDPS4A | 203700 | 2 |
| MITOCHONDRIAL MYOPATHY | 251900 | 1 |
| MITOCHONDRIAL SHORT-CHAIN ENOYL-COA HYDRATASE 1 DEFICIENCY; ECHS1D | | 5 |
| MOEBIUS SYNDROME 1; MBS1 | 157900 | 1 |
| MOLYBDENUM COFACTOR DEFICIENCY | 252150 | 1 |
| MOSAIC VARIEGATED ANEUPLOIDY SYNDROME 2; MVA2 | | 4 |
| MOSAIC VARIEGATED ANEUPLOIDY SYNDROME; MVA | 257300 | 5 |
| MOTOR NEURON DISEASE | | 1 |
| MUCOLIPIDOSIS II; ML2; ML II | 252500 | 15 |
| MUCOLIPIDOSIS III, COMPLEMENTATION GROUP C | 252605 | 2 |
| MUCOLIPIDOSIS IIIA | 252600 | 11 |
| MUCOLIPIDOSIS IV | 252650 | 8 |
| MUCOPOLYSACCHARIDOSIS TYPE II | 309900 | 25 |
| MUCOPOLYSACCHARIDOSIS TYPE IIIA | 252900 | 16 |
| MUCOPOLYSACCHARIDOSIS TYPE IIIB | 252920 | 5 |
| MUCOPOLYSACCHARIDOSIS TYPE IIIC | 252930 | 2 |
| MUCOPOLYSACCHARIDOSIS TYPE IIID | 252940 | 2 |
| MUCOPOLYSACCHARIDOSIS TYPE IVA | 253000 | 5 |
| MUCOPOLYSACCHARIDOSIS TYPE IVB | 253010 | 5 |
| MUCOPOLYSACCHARIDOSIS TYPE VI | 253200 | 21 |
| MUCOPOLYSACCHARIDOSIS TYPE VII | 253220 | 8 |
| MUCOPOLYSACCHARIDOSIS, TYPE IX; MPS9 | 601492 | 1 |
| MULIBREY NANISM | 253250 | 3 |
| MULTI-FOCAL DYSTONIA | | 227 |
| MULTICENTRIC CARPOTARSAL OSTEOLYSIS SYNDROME; MCTO | 166300 | 2 |
| MULTIPLE CONGENITAL ANOMALIES-HYPOTONIA-SEIZURES SYNDROME 1; MCAHS1 | | 1 |
| MULTIPLE ENDOCRINE NEOPLASIA, TYPE I; MEN1 | 131100 | 1 |
| MULTIPLE ENDOCRINE NEOPLASIA, TYPE II; MEN2 | 171400 | 7 |
| MULTIPLE ENDOCRINE NEOPLASIA, TYPE IIB; MEN2B | 162300 | 1 |
| MULTIPLE SCLEROSIS; MS | 126200 | 15 |
| MULTIPLE SULFATASE DEFICIENCY | 272200 | 7 |
| MULTIPLE SYSTEM ATROPHY | | 53 |
| MULTIPLE VASCULAR DISRUPTION SYNDROME | | 1 |
| MUSCULAR DYSTROPHY, CONGENITAL, LMNA-RELATED | | 1 |
| MUSCULAR DYSTROPHY, DUCHENNE TYPE; DMD | 310200 | 73 |
| MUSCULAR DYSTROPHY, LIMB-GIRDLE, TYPE 2A; LGMD2A | 253600 | 4 |
| MUSCULAR DYSTROPHY, PROGRESSIVE WITH CNS INVOLVEMENT & RECESSIVE INHERITANCE | | 1 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH BRAIN AND EYE ANOMALIES), TYPE A, 1; MDDGA1 (WALKER-WARBURG SYNDROME INCLUDED) | 236670 | 3 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH BRAIN AND EYE ANOMALIES), TYPE A, 2; MDDGA2
| | 2 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH BRAIN AND EYE ANOMALIES), TYPE A, 3; MDDGA3 | 253280 | 3 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH BRAIN AND EYE ANOMALIES), TYPE A, 6; MDDGA6 (WALKER-WARBURG SYNDROME INCLUDED) | | 1 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH BRAIN AND EYE ANOMALIES), TYPE A, 7; MDDGA7 | | 3 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY (CONGENITAL WITH MENTAL RETARDATION), TYPE B, 2; MDDGB2 | | 3 |
| MUSCULAR DYSTROPHY-DYSTROGLYCANOPATHY, TYPE B1 OR TYPE C1 | | 1 |
| MYASTHENIA GRAVIS; MG | 254200 | 8 |
| MYASTHENIC SYNDROME, CONGENITAL, ASSOCIATED WITH EPISODIC APNEA | 254210 | 1 |
| MYELOMA, MULTIPLE AMYLOIDOSIS, PRIMARY, INCLUDED; AL, INCLUDED | 254500 | 6 |
| MYHRE SYNDROME; MYHRS | 139210 | 2 |
| MYOCLONIC EPILEPSY NEONATAL WITH SUPPRESSION-BURST PATTERN | 609304 | 1 |
| MYOCLONIC EPILEPSY OF LAFORA | 254780 | 2 |
| MYOCLONIC EPILEPSY, JUVENILE; EJM1 | 254770 | 3 |
| MYOCLONIC-ATONIC EPILEPSY; MAE | | 4 |
| MYOCLONUS EPILEPSY ASSOCIATED WITH RAGGED-RED FIBERS; MERFF | 545000 | 2 |
| MYOPATHY DUE TO MYOADENYLATE DEAMINASE DEFICIENCY; MMDD | | 6 |
| MYOPATHY WITH GIANT ABNORMAL MITOCHONDRIA | 255140 | 1 |
| MYOPATHY, CENTRONUCLEAR, 1; CNM1 | 160150 | 13 |
| MYOPATHY, CONGENITAL, WITH FIBER-TYPE DISPROPORTION; CFTD | 255310 | 3 |
| MYOPATHY, CONGENITAL; TYPE UNKNOWN | | 8 |
| MYOPATHY, DISTAL, 5; MPD5 | | 5 |
| MYOTUBULAR MYOPATHY 1; MTM1 | 310400 | 13 |