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- TAU syndrome
- TEMPI syndrome
- Tabatznik syndrome
- Tang Hsi Ryu syndrome
- Tarsal tunnel syndrome
- Tay syndrome
- Teebi Kaurah syndrome
- Teebi Naguib Al Awadi syndrome
- Telangiectasia - Erythrocytosis - Monoclonal Gammopathy - Perinephric-Fluid Collections - Intrapulmonary Shunting
- Telomere biology disorder
- Teratoma with malignant transformation
- Testosterone 17-beta-dehydrogenase deficiency
- Tetraamelia with ectodermal dysplasia and lacrimal duct abnormalities
- Tetrahydrobiopterin deficiency
- Tetrahydrofolate-methyltransferase deficiency syndrome
- Tetralogy of Fallot
- Tetraploidy
- Tetrasomy 18p
- Tetrasomy X
- teunissen-cremers syndrome