[The biochemistry of psoriasis].

Numerous general metabolic systems are disturbed in association with psoriasis: the frequency of diabetes mellitus and of hyperuricaemia, lipid disturbances and a decrease in folates as a result of their excessive consumption by the skin. Cutaneous metabolism is also altered. Numerous compounds are formed in excess from glucose: amino acids, fatty acids and sterols, lactic acid--the formation of which persists in the corneal layer, ribose and ribulose--synthesised as a result of glucose-6-phosphate-dehydrogenase hyperactivity (role of the increased catabolism of dehydro-epi-androsterone) and uronic acids. The accumulation of glycogen is probably due to excessive synthesis and impaired breakdown. These abnormalities may exist to a lesser extent in healthy skin. In the corneal layer there are lipid vacuoles visible under the electron microscope. Lipogenesis is increased. The same may apply to lipolysis (blood NEFA are increased). Esterification of cholesterol is decreased. The utilisation of ATP by cell membranes is probably diminished (low ATP ase activity). The absence of formation of keratohyaline is due to persistence of the repression which normally prevents it in the mucus body. Renewal of collagen appears increased. The synthesis of DNA is increased in the lesions and neighbouring areas. It is possible that these various abnormalities are dependent upon modifications in the regulator systems of cyclic AMP and GMP, variations in which are however discussed.