Brain metabolism (relative bilateral increases in thalamic, occipital and cerebellar glucose metabolism associated with bilateral decreases in striatal [18F]FDG binding), postsynaptic dopaminergic function (reduction in striatal and cortical D1 receptor [11C]SCH22390 binding and D2 receptor [11C]raclopride binding) and PDE10A levels (reduction in striatal and pallidal [11C]IMA107 binding and increase in motor thalamic nuclei [11C]IMA107 binding) have been shown to be powerful biomarkers for assessing progression in patients with manifest HD and also during premanifest stages. The gene discussed is PDE10A; the disease is Huntington disease.