See Rare Diseases by First Letter (G)
- Galactorrhoea-Hyperprolactinaemia
- Galactose Epimerase Deficiency
- Galactosemia
- Galactosialidosis
- Gall Bladder Cancer
- Ganglioglioma
- Gardner Syndrome
- Gastric Lymphoma
- Gastro-enteropancreatic Neuroendocrine Tumor
- Gastrointestinal Stromal Tumors
- Gastroschisis
- Gaucher Disease
- Gaucher Disease Type 1
- Gaucher Disease Type 2
- Gaucher Disease Type 3
- Gelatinous Ascites
- Genital Dwarfism
- Geographic Tongue
- Germinoma
- Gestational Trophoblastic Tumor
- Giant Axonal Neuropathy
- Giant Cell Arteritis
- Giant Cell Myocarditis
- Giant Papillary Conjunctivitis
- Gigantism
- Gigantomastia
- Gitelman Syndrome
- Glanzmann Thrombasthenia
- Glaucoma 3 Primary Infantile B
- Glaucoma, Congenital
- Glioblastoma
- Glioma
- Gliomatosis Cerebri
- Gliosarcoma
- Glomerulonephritis
- Glucagonoma
- Glucagonoma Syndrome
- Glucocorticoid-remediable Aldosteronism
- Glucose-6-phosphate Dehydrogenase Deficiency
- Glycogen Storage Disease Type 2
- Glycogen Storage Disease Type 3
- Glycogen Storage Disease Type 4
- GM1 Gangliosidosis
- Gonadal Dysgenesis
- Granulocytopenia
- Granuloma Annulare
- Granulosa Cell Tumor of the Ovary
- Graves' Disease
- Gray Platelet Syndrome
- Griscelli Syndrome
- Growth Hormone Deficiency
- Guillain-Barre Syndrome
- Gyrate Atrophy of Choroid and Retina