Also, higher levels of dopamine D2 receptor occupancy were found in the basal ganglia of TD patients carrying the W317X mutations, the Hdc knockout mice and the Hdc heterozygous mice, indicating that the dopamine release in the basal ganglia of the brain might be disinhibited due to histamine depletion (28). The gene discussed is DRD2; the disease is thanatophoric dysplasia.