See Rare Diseases by First Letter (L)
- Lactate Dehydrogenase A Deficiency
- Lafora Disease
- Lambert Eaton Myasthenic Syndrome
- Lamellar Ichthyosis
- Landau-Kleffner Syndrome
- Langerhans Cell Histiocytosis
- Large B Cell Diffuse Lymphoma
- Large Granular Lymphocyte Leukemia
- Laron Syndrome
- Laryngeal Cancer
- Laryngeal Cleft
- Laryngeal Papillomatosis
- Laryngomalacia
- Lassueur-Graham-Little Syndrome
- LCAD Deficiency
- LCHAD Deficiency
- Leber Congenital Amaurosis
- Leber Congenital Amaurosis 2
- Leber Hereditary Optic Neuropathy
- Leber Miliary Aneurysm
- Left Ventricular Noncompaction
- Legg-Calve-Perthes Disease
- Legionellosis
- Leigh Syndrome
- Leiner Disease
- Leiomyomatosis and Renal Cell Cancer, Hereditary
- Leiomyosarcoma
- Leishmaniasis
- Lentigo Maligna Melanoma
- Leptospirosis
- Lesch Nyhan Syndrome
- Leukemia, B-cell, Chronic
- Leukemia, Myeloid
- Leukemia, T-cell, Chronic
- Leukodystrophy
- Leukomalacia
- Leukoplakia
- Levator Syndrome
- Lewy Body Dementia
- Li-Fraumeni Syndrome
- Lichen Planus Follicularis
- Lichen Sclerosus
- Liddle Syndrome
- Light Chain Deposition Disease
- Limb-girdle Muscular Dystrophy
- Limb-girdle Muscular Dystrophy Type 2H
- Limb-girdle Muscular Dystrophy, Type 2A
- Limb-girdle Muscular Dystrophy, Type 2B
- Limb-girdle Muscular Dystrophy, Type 2C
- Limbic Encephalitis
- Lip and Oral Cavity Cancer
- Lipodystrophy
- Lipogranulomatosis
- Liposarcoma
- Listeria Infection
- Liver Cancer
- Localized Scleroderma
- Locked-in Syndrome
- Loeys-Dietz Syndrome
- Logopenic Progressive Aphasia
- Loiasis
- Long QT Syndrome 1
- Lowe Oculocerebrorenal Syndrome
- Lupus Nephritis
- Lymph Node Neoplasm
- Lymphangiectasis
- Lymphangioleiomyomatosis
- Lymphangioma
- Lymphangiomatosis
- Lymphatic Filariasis
- Lymphoblastic Lymphoma
- Lymphocytic Colitis
- Lymphoma AIDSrelated
- Lymphoma, Large-cell
- Lymphoma, Large-cell, Immunoblastic
- Lymphoma, Small Cleaved-cell, Diffuse
- Lymphoma, Small Cleaved-cell, Follicular
- Lymphomatoid Granulomatosis
- Lymphomatoid Papulosis
- Lymphomatous Thyroiditis
- Lymphosarcoma
- Lynch Syndrome