HD-CSF (Studying cerebrospinal fluid to understand key CNS pathobiological targets in Huntington's disease) is a longitudinal observational study. At baseline participants will attend a Screening Visit and Sampling Visit (collectively referred to as Core Baseline activities) and may attend an optional third visit (optional Repeat Sampling Visit). At follow-up 24 months later the screening Visit, sampling (collectively referred to as Core Follow-up activities) and optional Repeat Sampling Visit will be repeated. During the Screening Visit, medical history, and clinical and phenotypic data including an optional MRI scan will be obtained. Participants who meet the eligibility requirements of the study and are willing to continue in the study, will return for a Sampling Visit. During that visit, biosamples will be collected following an overnight fast: blood will be obtained via venepuncture and CSF will be obtained via lumbar puncture. Some participants may be invited to return for a Repeat Sampling Visit approximately 4-8 weeks later. Participant cohorts are as follows: 1. Healthy controls, n= 20 2. Pre-manifest HD, n=20 3. Early to moderate manifest HD, n = 40