Pathophysiology of premature aging characteristics in Mendelian progeroid disorders.

Aging is a physiological process that is in part genetically determined. Some of the signs and symptoms of aging also occur prematurely in Mendelian disorders. Such disorders are excellent sources of information of underlying mechanisms for these components of aging, and studying these may allow detection of pathways that have not yet considered in detail in physiological aging. Here I define the clinical characteristics that constitute aging and propose that at least 40% of aging signs and symptoms should be present before an entity should be tagged as progeroid. A literature search using these characteristics yields 17 entities that fulfill this definition: Hutchinson-Gilford progeria, mandibulo-acral dysplasia, Nestor-Guillermo progeria, Werner syndrome, Cockayne syndrome, cutis laxa progeroid, Penttinen progeroid syndrome, Mandibular underdevelopment, Deafness, Progeroid features, Lipodystrophy, Fontaine progeroid syndrome, SHORT syndrome, Wiedemann-Rautenstrauch syndrome, Mulvihill-Smith syndrome, dyskeratosis congenita, Marfan syndrome lipodystrophy type, Warburg-Cinotti syndrome, Lessel syndrome and Bloom syndrome. The presenting and main characteristics of these entities are indicated briefly. Their pathophysiology is not complete pathophysiology is reviewed but only the pathophysiology of the premature aging characteristics of this series of entities is compared to the known mechanisms ("Hallmarks") of physiological aging as summarized in the review paper by Lopez-Otin and colleagues. Although many causative genes have not been studied fully for all known aging mechanisms the comparison demonstrates that additional mechanisms must play a role to explain the aging characteristic in some of the progeroid entities of the progeroid entities, and possibly also in physiological aging.