Erythema dyschromicum perstans (EDP), described by Convit et al. in 1961, is a rare dermatosis. Its relationship with ashy dermatosis (AD), described by Ramirez in 1957, is still a matter of debate. We report a typical case of EDP. The patient, of North African origin, had a dyschromic (hypo- and hyperpigmented) eruption on the chest and limbs for 2 years. The lesions were occasionally surrounded by a papular border which spread slowly and centrifugally. Histological examination showed a lichenoid infiltrate. A carcinoma of the lung was simultaneously discovered. No treatment was given, EDP is infrequent and often considered identical to ashy dermatosis in the literature. However, the clinical aspects of the two diseases differ. The main features of these two diseases are reviewed and compared on the basis of a literature review. We conclude that EDP and AD are distinct clinical entities.

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The development of quantitative correlations between the physicochemical properties of compound and its ability to act as a skin sensitizer is complicated by the number of variables associated with the current sensitization lest data, combined with the absence of truly objective end point. Recently, however, a novel approach to die assessment of skin sensitization potential, the local lymph node assay (LLNA). has been described, which determines the skin sensitization by measuring lymphocyte proliferation in lymph nodes draining the site of chemical exposure. The assay offers several advan‐tages over traditional methods in the context of quantitative structure‐activity relationship studies. In the present work, H range of bromoalkanes has been employed which demonstrate the robustness and reproducibility of the LLNA. Sensitizing activity increased with chain length up to a maximum at C15/C116. whereafter the response declined. The data were modelled against hydrophobicity. expressed as Clog P and (ClogP)2 to fit the biphasic nature of the results. The results dermonstrate the utility of LLNA data for interpretation in the context Off quantitative: structure‐activity relationships, the limited number of variables, inter‐test reproducibility and quantitative end point, lending themselves to mathematical interpretations.