Sweat duct proliferation associated with aggregates of elastic tissue and atrophodermia vermiculata: a simulator of microcystic adnexal carcinoma. Report of two cases.

Microcystic adnexal carcinoma (MAC) is a rare, usually solitary, slowly growing, yet aggressive neoplasm with a tendency for local recurrences. Herein, we present two patients who had been histopathologically diagnosed as suffering from MAC on both cheeks since childhood, an unlikely scenario. Both from a clinical and from a histopathological point of view, our two cases showed some similarities with those previously described in patients with Nicolau-Balus syndrome, Rombo syndrome, and so-called eccrine-pilar hamartoma. Common to all these latter disorders are the round aggregations of elastic tissue in the papillary dermis, a histopathological feature which was also found in our patients. However, to our knowledge, the presence of a MAC-like ductal proliferation embedded in sclerotic stroma and extending to the deep dermis has not been previously described. Dermatologists and dermatopathologists should be aware of this disorder to avoid overdiagnosis of and inappropriate treatment for MAC.

The time course of photoadaptation and pigmentation studied using a novel method to distinguish pigmentation from erythema.

The dynamics of human pigmentation in response to ultraviolet radiation (UVR) remain poorly characterized. In part, this is attributable to methodological issues relating to the overlap in spectra of hemoglobin and melanin. We describe a new method, based on the recording of reflectance properties following iontophoresis of a potent vasoconstrictor, noradrenaline. This removes the influence of blood, allowing measurement of pigmentation, represented as L* on the L*a*b* scale. Blood flow was separately assessed using laser Doppler flowmetry. We show that there is a clear dose response with the dose of UVR administered, that pigmentation peaks at 1 wk and declines over the following 10 wk, but does not return to baseline within this period. We show clear differences in the degree, but not the temporal pattern of pigmentation between different pigmentary groups. We also report that the relation between facultative pigment and constitutive pigment is incomplete, with a wide scatter of responses for the development of pigmentation irrespective of constitutive levels. For comparison we also document overall photoadaptation and relate changes in pigmentation to the overall changes in photoadaptation.

Quantitative measures of the effect of the melanocortin 1 receptor on human pigmentary status.

Variation in human hair and skin color is the most striking visible aspect of human genetic variation. The only gene known to exert an effect on pigmentary within the normal population is the melanocortin-1 receptor (MC1R). Previous studies have used a Mendelian framework to relate MC1R genotype to phenotype, by measuring pigmentary status using categorical scales. Such approaches are inadequate. We report results using direct measures of hair color using objective colorimetric dimensions and HPLC determined hair melanins. We have linked MC1R genotype with chemical measures of melanin quantity and type and objective phenotype measures of color. MC1R genotype was predictive of hair melanin expressed as the ratio of the loge of eumelanin to pheomelanin ratio, with a dosage effect evident: MC1R homozygote mean, 1.46; heterozygote, 4.44; and wild type, 5.81 (p<0.001). Approximately 67% of the variance in this model could be accounted for in terms of MC1R genotype. There was also a relation between MC1R status and hair color, most prominently for the b* axis (p<0.001), but also for the a* and L* scales (L*a*b*, CIE). We show for one of the most polymorphic human traits that it is possible to demonstrate meaningful relations between various physical characteristics: DNA sequence diversity, hair-wavelength-specific reflectance patterns, and chemical melanin assays.