- Leakage
- Leaky heart - see Endocarditis
- Learning defect, specific NEC (strephosymbolia) 315.2
- Leather bottle stomach (M8142/3) 151.9
- Leber's
- Lederer's anemia or disease (acquired infectious hemolytic anemia) 283.19
- Lederer-Brill syndrome (acquired infectious hemolytic anemia) 283.19
- Leeches (aquatic) (land) 134.2
- Left-sided neglect 781.8
- Leg - see condition
- Legal investigation V62.5
- Legg (-Calvé)-Perthes disease or syndrome (osteochondrosis, femoral capital) 732.1
- Legionnaires' disease 482.84
- Leigh's disease 330.8
- Leiner's disease (exfoliative dermatitis) 695.89
- Leiofibromyoma (M8890/0) - see also Leiomyoma
- Leiomyoblastoma (M8891/1) - see Neoplasm, connective tissue, uncertain behavior
- Leiomyofibroma (M8890/0) - see also Neoplasm, connective tissue, benign
- Leiomyoma (M8890/0) - see also Neoplasm, connective tissue, benign
- Leiomyomatosis (intravascular) (M8890/1) - see Neoplasm, connective tissue, uncertain behavior
- Leiomyosarcoma (M8890/3) - see also Neoplasm, connective tissue, malignant
- Leishmaniasis 085.9