ABSTRACT
Dementia in younger people (young onset dementia, YOD) is increasingly recognised as an important clinical and social problem, with frequently devastating consequences for both the sufferer and those who care for them.1 Prevalence rates of YOD have been estimated between 67 to 81 per 100 000 in the 45 to 65 year old age group;2,3 thus there are currently approximately 10 000 patients with YOD in the United Kingdom alone. YOD poses a diagnostic challenge and may present with a wide variety of subtle behavioural, cognitive, psychiatric, or neurological symptoms. While the degenerative dementias characteristically affect older patients, they are also an important cause of YOD: indeed, Alzheimer's disease is the commonest single cause of YOD with an estimated 3000 cases in the United Kingdom, followed by vascular dementia and the frontotemporal lobar degenerations (see Table 15.1). The young onset forms of these diseases are frequently familial.4 Some degenerative dementias such as variant Creutzfeldt-Jakob disease typically occur in the young patient. In contrast, Lewy body dementia, which accounts for 20% of cases in patients over 65 years of age, accounts for only a small proportion of YOD.
