- Ménière disease
- M.E.N.1
- M.E.N.2A
- M.E.N.2B
- Maagkanker
- Macroglobulinemie van Waldenström
- Macula dystrofie
- Maculadegeneratie
- Male Turner Syndrome
- Malformatiesyndroom
- Maligne epitheliale tumor van de speekselklieren
- Maligne mesenchymale tumor
- Maligne wekedelentumor
- MALT-lymfoom
- MALToom
- Mandibulofaciale dysostosis
- MAP
- Marfan syndrome
- Marfansyndroom
- Marie-Strumpell spondylitis
- Markesberry myopathie
- Markesberry spierdystrofie
- Marshall-Smith Syndroom
- Marshallsyndroom met periodieke koorts
- Martin-Bell syndroom
- Mastocytose
- Maternale fenylketonurie
- Maternale phenylketonurie
- Maternale PKU
- Maturity-Onset Diabetes of the Young
- Mayer-Rokitansky-Küster Syndroom
- Mayer-Rokitansky-Küster-Hauser Syndroom
- Mazabraud syndroom
- MC
- MCAD-deficiëntie
- MCADD
- McArdle disease
- McCune Albrightsyndroom
- McCune-Albrightsyndroom
- McKusick type chondrodysplasie
- MCL
- MCTD
- MD
- MD
- MD type 1
- MD2
- MDS
- MEA
- Meadowssyndroom
- Meckel-Grubersyndroom