See Rare Diseases by First Letter (I)
- I Cell Disease
- IBIDS Syndrome
- Ichthyosis Linearis Circumflexa
- Ichthyosis Vulgaris
- Idiopathic Adolescent Scoliosis
- Idiopathic Myopathy
- Idiopathic Pulmonary Fibrosis
- Idiopathic Pulmonary Hemosiderosis
- Idiopathic Pulmonary Hypertension
- Idiopathic Thrombocytopenic Purpura
- Immune Thrombocytopenia
- Immunodeficiency With Hyper IgM Type 1
- Inborn Amino Acid Metabolism Disorder
- Inclusion Body Myopathy 2
- Inclusion Body Myositis
- Inclusion Conjunctivitis
- Incontinentia Pigmenti
- Indolent B Cell Lymphoma
- Infantile Apnea
- Infantile Scoliosis
- Infantile-onset Ascending Hereditary Spastic Paralysis
- Infectious Arthritis
- Infective Endocarditis
- Inflammatory Breast Cancer
- Inflammatory Myofibroblastic Tumor
- Insulin-like Growth Factor I Deficiency
- Insulinoma
- Intestinal Pseudo-obstruction
- Intracranial Arteriovenous Malformation
- Intrahepatic Cholangiocarcinoma
- Intrahepatic Cholestasis of Pregnancy
- Intraocular Melanoma
- Intrauterine Infections
- Intravenous Leiomyomatosis
- Iridocorneal Endothelial Syndrome
- Isaac's Syndrome
- Isolated ACTH Deficiency