SV2A and Huntington disease: Taken together with a recent positron emission tomography (PET) imaging study that found specific loss of the presynaptic protein SV2A in the caudate and putamen of premanifest HD patients158, these results demonstrate that changes in complement biology and loss of synaptic markers occur in the central nervous system (CNS) of patients with HD before symptom onset and, thus, that the elimination mechanism that we describe may already be operating at this stage of the disease.