Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Accelerated aging diseases are diseases that can clinically resemble some aspects of accelerated aging, for example the Hutchinson-Gilford Progeria or the Werner syndrome, nearly all caused by DNA repair defects. Because the accelerated aging diseases display different aspects of aging, but never every aspect, they are often called segmental progerias by biogerontologists. Against this position other biogerontologists argue that premature aging phenotypes are identifiable symptoms associated with mechanisms of molecular damage. The fact that these phenotypes are widely recognized justifies classification of the relevant diseases as "accelerated aging". Learn more about the various illnesses commonly referred to as accelerated aging diseases in this book.