30 TESTING
Keratosis pilaris quantified by two test methods
n Doridot E, Bondil C, Pinard E, Leonard M, Mondon P, PhD – Sederma, France
Keratosis pilaris (KP) is one of the most common skin imperfections that results from follicular hyperkeratosis. It is characterized by an accumulation of corneocytes forming a keratinized plug which blocks and then dilates the hair follicle, sometimes associated with perifollicular erythema 1
(Figs 1-2). Because
of its bad cosmetic appearance, KP can be socially disabling.2 Prevalence for KP is almost 40% of the total population and is increased in adolescents, predominantly girls where the prevalence is up to 80%. Studies show this phenomenon occurs in more than 85% of cases during the first two decades of life, mainly on arms, legs and buttocks. This condition is quite often familial (39 to 67% of the cases according to the authors) although no single gene mutation has yet been directly associated with keratosis pilaris. If KP reduces with age in 35% of people, it remains at the same level in 43% of the cases and even worsens for the others.1,3 There are, however, more or less strong
correlations between certain states of life or pathologies and keratosis pilaris occurrence. Obesity, diabetes, pregnancy, menopause and vitamin A deficiency are thus unfavorably associated with keratosis pilaris.4,5
Keratosis pilaris is also more
common for people with cutaneous dryness (ichthyosis vulgaris and atopic dermatitis), with a less efficient skin barrier and less retention of epidermal water, moreover 35% of KP patients displayed common mutations in filaggrin gene.6 On the other hand, an environmental aspect might play a role, as keratosis pilaris regresses during summer and worsens during winter cold dry episodes.2,3,7
This
suggests that the air humidity reduction can be considered as an aggravating factor. Metrological evaluation of KP is not a developed field and only a few visual observations are available in scientific literature. In order to better quantify, illustrate and describe morphological parameters of KP, development of two methods were performed. The first method consisted in an
PERSONAL CARE NORTH AMERICA Figure 1: Schematic illustrating skins without (left) or with keratosis pilaris (right).
Figure 2: Visual examples of keratosis pilaris appearance.
acquisition with a dermatoscopic camera which provides standardized 2D pictures and 3D representations. The second method used negative prints (replicas) of the KP. An acquisition of the replicas relief was performed by fringe projection technology and then, analyzed with the Dermatop software AEVA or with software MOUNTAINS. Two specific process were developed within both software in order to calculate parameters such as density, surface, perimeter, volume and thickness. Thanks to this preliminary development, the cosmetic effect of a cream containing a Salinicoccus hispanicus lysate filtrate versus a placebo was evaluated.
Materials and methods Panel for development of the method 21 Caucasian female volunteers aged 24-54
years (mean 39 y.) with visible KP were recruited, 63 different KP sites were isolated and analyzed in four body parts (35% on upper part of leg, 41% on lowest part of leg, 22% on knees, 2% on arms).
Panel for product evaluation & design of the study
16 female volunteers aged 19-49 years (mean 35 y.) with visible KP were recruited. Among these volunteers, 13 were tested for KP on legs and 3 for KP on arms. All subjects were informed about the objective of the study and endorsed an informed consent. The study has been approved by an internal ethic committee and was conducted under medical control respecting the spirit of Good Clinical Practice (GCP). Volunteers were asked to stop scrubs and moisturizing creams on
March 2020
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