- Lown (-Ganong)-Levine syndrome (short P-R interval, normal QRS complex, and paroxysmal supraventricular tachycardia) 426.81
- LSD reaction (see also Abuse, drugs, nondependent) 305.3
- Lucas-Championnière disease (fibrinous bronchitis) 466.0
- Lucey-Driscoll syndrome (jaundice due to delayed conjugation) 774.30
- Ludwig's
- Lues (venerea), luetic - see Syphilis
- Luetscher's syndrome (dehydration) 276.51
- Lumbago 724.2
- Lumbalgia 724.2
- Lumbar - see condition
- Lumbarization, vertebra 756.15
- Lumbermen's itch 133.8
- Lump - see also Mass
- Lunacy (see also Psychosis) 298.9
- Lunatomalacia 732.3
- Lung - see also condition
- Lupoid (miliary) of Boeck 135
- Lupus 710.0
- 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