- Luschka's joint disease 721.90
- Luteinoma (M8610/0) 220
- Lutembacher's disease or syndrome (atrial septal defect with mitral stenosis) 745.5
- Luteoma (M8610/0) 220
- Lutz-Miescher disease (elastosis perforans serpiginosa) 701.1
- Lutz-Splendore-de Almeida disease (Brazilian blastomycosis) 116.1
- Luxatio
- Luxation - see also Dislocation, by site
- Lycanthropy (see also Psychosis) 298.9
- Lyell's disease or syndrome (toxic epidermal necrolysis) 695.15
- Lyme disease 088.81
- Lymph
- Lymph-hemangioma (M9120/0) - see Hemangioma, by site
- Lymphadenitis 289.3
- Lymphadenoid goiter 245.2
- Lymphadenopathy (general) 785.6
- Lymphadenopathy-associated virus (disease) (illness) (infection) - see Human immunodeficiency virus (disease) (illness) (infection)
- Lymphadenosis 785.6
- Lymphangiectasis 457.1
- Lymphangiectatic elephantiasis, nonfilarial 457.1
- Lymphangioendothelioma (M9170/0) 228.1
- Lymphangioleiomyomatosis 516.4
