Microsoft Word - DRM175BF.rtf

Author’s address: J.W.H. Mali, Javastraat 104, Nijmegen (The Netherlands) Last year some doubt arose about the real significance of the positive patch test for bichromate solutions, as positive patch tests and intra-cutaneous reactions for trivalent chromium compounds have been reported (Fregert et al.) and because trivalent chromium compounds, next to bichromate have often been found in the environment of patients. The dispute centres around two different problems: Are trivalent Cr compounds of importance in the sensitization process ? Do they have a practical significance in the pathogenesis of the chromium dermatitis ? Ad (1): In our opinion, sensitization is not caused by bichromate but by a reduced, presumably trivalent compound originating in the dermis. Arguments in favour of this hypothesis may be found in the fact that bichromate salts are rather easily reduced by substances in epidermis and dermis. Moreover, Van Neer succeeded in sensitizing guinea-pigs to bichromate by injecting trivalent Cr compounds. In addition, in some guinea-pigs heavily sensitized by sensitization with Hunzíker, s method (bichromate + Freund adjuvans), circulating antibodies against trivalent Cr were demonstrated. The most important argument for the specific role of trivalent compounds are the positive reactions on intracutaneously injected trivalent Cr. The intensity of these reactions, however, remains much smaller than that on intracutaneously injected bichromate, if one uses the same concentration. It is possible that the different reactions are determined by the difference in chemical and physical properties between triand hexa176 Mali, Chromium or Chromate Dermatitis valent Cr compounds. The permeability of whole skin in vivo and in vitro or chromium sulfate and chromium chloride is for instance 10,000 × smaller than for bichromate (Spruit). The affinity of the trivalent Cr compounds to the skin proteins is much larger than that of the hexavalent (Mali, van Kooten, van Neer). Spruit however demonstrated that the very small concentrations of bichromate, which are encountered in the environment of the patient in real-life conditions are for the larger part detained in the dermal tissue by absorption. By this mechanism a minimum concentration, necessary for the initiation of sensitivity, may be built up in the dermis. Van Neer’s recent experiments on pigs demonstrate the difficulty of using animal experiments in order to explain the mechanism of sensitization. Pigs are much more easily sensitized than guinea-pigs, the sensitization of man being somewhere in between. It may however be possible