Hypotonia, Ataxia, Developmental Delay, and Tooth Enamel Defect Syndrome (HADDTS) is an exceptionally rare disorder resulting from a heterozygous variant in the C-terminal binding protein 1 (CTBP1) gene. The gene discussed is CTBP1; the disease is hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome.