XANTHOPATHY (Latin pigmentum paint) — adjournment in skin of the colorants giving it a certain coloring. Distinguish normal and pathological the Item. Normal skin of the person contains five pigments; melanin, melanoid, carotene, oxyhemoglobin and the recovered hemoglobin. Their quantitative ratios in various sites of skin vary. It is more carotene in palms and soles; skin of nipples, a century, scrotums is especially rich with melanin.
The greatest value has adjournment in skin of melanin (see. Melanina ). A melanogenesis — the complex process of oxidation of colourless substances happening in pigment cells (see), called by melanocytes. It is carried out by specialized cytoplasmatic organellas (melanosoma) containing specific enzyme a tyrosinase. Substrate for formation of melanin is the amino acid (tyrosine) turning under the influence of a tyrosinase into DOFA, or the pro-melanin which is polymerized in melanin. The melanogenesis is regulated melanotsitostimuliruyushchy hormone (see), the developed hypophysis, and also adrenaline and noradrenaline, hormones thyroid and gonads. Disturbance of a melanogenesis leads or to excess accumulation of a pigment, napr, at addisonovy disease (see), acanthosis nigricans (see), or to decrease or lack of its contents — the depigmentation most often connected with inborn dysfunction of melanoblasts (predecessors of melanocytes). Depigmentation can be inborn — albinism (see) and acquired — a leukoderma at syphilis, the prof. vrednost and at use of some pharmaceuticals (see. Leukoderma ).
Bibliography: Babayants R. S. and Lonshakov Yu. I. Frustration of a xanthopathy, page 20, M., 1978; With t r at-to about in A. I. and Serov V. V. Pathological anatomy, page 43, M., 1979: The metabolic basis of inherited disease, ed. by J. B. Stanbury a. o., p. 283, L., 1978.
G. M. Tsvetkova.