Variation in skin thickness may explain some of the within-person variation in ultraviolet radiation-induced erythema at different body sites.
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Erythema↗
Biomedical subjects
Karen Waterston
Publications and source records attributed to Karen Waterston.
Measurement of itch using actigraphy in pediatric and adult populations.
We have studied nocturnal movements using wrist-worn accelerometers in 33 adults with a range of pruritic dermatoses, 30 adult control subjects, 25 children with atopic dermatitis, and 17 pediatric control subjects. In all, 26 adults and 20 children were studied on more than one occasion, up to a maximum of 6 occasions. Participants were examined and a range of subjective measures about the extent of skin disease, itch, and quality of sleep were recorded. We show clear differences between patients and control subjects for both age groups studied, with activity medians approximately twice as high in the patients as in the control subjects ( P < .001). Studies on the same person show a considerable night-to-night variation that is unlikely to relate to measurement error, but instead, we believe, reflect genuine differences in nocturnal activity (and perhaps disease severity). Movement through the night did not seem to follow any obvious pattern. The relation between subjective measures, Severity sCORing of Atopic Dermatitis (SCORAD) index scores, and objective recorded activity was imperfect, with much unaccounted for variation. In particular, in adults, but not in children, we found a negative correlation (-0.44, P < .02) between objective movement activity and self-reported quality of sleep. Our results support the use of objective measures of scratch in the assessment of disease activity, and suggest that the relation between subjective and objective measures of disease severity may not be straightforward.
Adolescent↗
The development of an objective method for measuring scratch in children with atopic dermatitis suitable for clinical use.
Itch is a major symptom of skin disease and remains poorly studied. We have used limb-worn digital accelerometers, and infrared video of patients as a gold standard, on children with atopic dermatitis and control subjects in their own homes at night. Video analysis shows that nocturnal scratching and restlessness are more complex than we first thought, with many movements that potentially damage the skin not conforming to stereotypical scratch movements. Children with atopic dermatitis spent a mean of 46 minutes less time motionless or sleeping at night than control subjects (468 +/- 3 [SEM] vs 422 +/- 37 [SEM], P<.001). Children with atopic dermatitis showed 2 to 3 times as much scratching or restlessness activity as control subjects, with little overlap between groups (P<.01). Scratching and restlessness were highly correlated with each other (0.94, P<.01). Accelerometer scores were highly correlated with video results (rho>0.02, P<.01, for scratching, restlessness, and sleeping time). Individual limb scores were highly correlated with each other (rho approximately 0.87-0.98), suggesting that little information would be lost if only 1 limb was measured. There was little relation between parental assessment of scratch and objective measured scratch. Accelerometers provide a useful and practical way of assessing scratching at night in the patient's own home and could be used as an objective measure of disease activity both in clinical trials and in everyday clinical practice.
Behavior↗
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.
Female↗
No association between p53 codon 72 polymorphisms and erythemal response.
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Erythema↗
Physiological variation in the erythemal response to ultraviolet radiation and photoadaptation.
We have studied the cutaneous response to ultraviolet radiation, measured objectively as erythema in a sample of 12 body sites on 15 Northern European subjects with multiple doses of ultraviolet B (UVB). Skin pigmentation and the development of photoadaptation in response to five repeated doses of irradiation at three body sites was also measured. We report striking differences of up to 5-fold at different body sites to the same challenge dose (p < 0.001) and demonstrate that for this population, site variation is just as important as between-person variation. Skin color at each body site is a strong predictor of response (p < 0.001) and that this cannot be attributed to vascular differences, but instead we believe it reflects site-specific variations in melanin pigmentation. We also observed similar but smaller within-person effects for responses to another inflammatory agent, dithranol (p < 0.01). Despite this, we did not find evidence for differences in the development of photoadaptation by body site. These results have clear clinical implications for the practice of phototesting prior to commencing phototherapy, for therapeutic failure in sites such as the legs in patients with psoriasis, and perhaps for melanoma body-site distribution.
Adaptation, Physiological↗
Time course of ultraviolet B-induced erythema in people with red hair harbouring homozygous melanocortin 1 receptor mutations.
It has previously been reported that the time course of erythema may be delayed in those with sun-sensitive skin types and those with skin cancer. One molecular explanation for this putative phenotype would be that it is caused by mutations of the melanocortin 1 receptor (MC1R). In the present study of 20 persons, 10 of whom were MC1R homozygous, we measured erythema over a 21-day period in response to a range of ultraviolet B doses using methods that improved on previous studies. We could detect no consistent differences in ultraviolet radiation-induced erythema between the groups studied. The pharmacological mechanisms underpinning such prolonged inflammatory responses merit further investigation.
Case-Control Studies↗
The relationship between constitutive pigmentation and sensitivity to ultraviolet radiation induced erythema is dose-dependent.
The relationship between skin colour and experimental exposure to ultraviolet radiation (UVR) B, with response measured as erythema was studied. Two reflectance methods were used to measure skin colour--tristimulus colorimetry using a Minolta instrument (summarized as the alpha characteristic angle) and the melanin index based on the Diastron reflectance instrument. As expected both measures are highly correlated (0.91). A dose-dependent relationship between skin colour measured as the alpha characteristic angle and UVR was established, with the gradient increasing from 0.99 at 119 mJ to 2.7 at 300 mJ, with the relevant standard errors being 0.39 and 0.47, respectively. Similarly, for the melanin index (where the scale goes in the opposite direction) the gradient differs between -0.49 for 119 mJ and -0.91 for 300 mJ, with the standard errors being 0.14 and 0.17 respectively. The proportion of variation explained is also greater at higher UVR challenge doses. Studies relating UVR sensitivity and pigmentation need to take account of the dose of UVR administered.
Dose-Response Relationship, Radiation↗