How dry I am: The white scale sign of xerosis
Dec. 22, 2016
When winter approaches my skin dries out. Fortunately, it doesn’t bother me at all. For others, especially in the elderly, xerosis be a predisposing factor for asteototic eczema, nummular dermatitis or dyshidrotic eczema (1). With so many people presenting with dry skin, it is easy to forget about thinking about associated conditions such as hypothyroidism or HIV. In severe cases (acquired ichthyosis), other considerations include underlying malignancies (especially lymphoproliferative disorders); autoimmune/inflammatory disorders (sarcoidosis, collagen vascular diseases, celiac disease), metabolic diseases (essential fatty acid deficiency, pancreatic insufficiency), endocrine abnormalities (hypopituitarism, hyperparathyroidism), infectious diseases (Hansen disease); and medication use (2). Severe xerosis is a frequent accompaniment of the ever-increasing number targeted therapies in oncologic patients (3).
Although predisposing factors are well-known, the precise etiology of xerosis remains to be defined, and may differ in various circumstances. It is a problem of barrier function of the stratum corneum (SC), which may be related to filaggrin mutations in those with an atopic diathesis. But what about the xerosis in the elderly? According to Biniek et al, with age the keratin filaments within corneocytes are prone to crosslinking, the amount of intercellular lipids decreases resulting in fewer lipid bilayers, and the rate of corneocyte turnover decreases. The effect of these structural changes on the mechanical properties of the SC has not been determined. The authors determined how several aspects of the SC’s mechanical properties dramatically degraded with age. By performing a range of biomechanical experiments, they demonstrated that the stratum corneum stiffens with age, indicating that the keratin fibers stiffen, similarly to collagen fibers in the dermis. The cellular cohesion also increases with age, a result of the altered intercellular lipid structure. The kinetics of water movement through the SC is also decreased, allowing the authors to conclude that the combination of structural and mechanical property changes that occur with age are quite significant and may contribute to the prevalence of skin disorders among the elderly (4).
Klemmer et al raise an interesting point — dry skin (xeroderma) is flaky, dry, and cracked, yet they state that “xeroderma lacks diagnostic criteria and signs.” I had never questioned my ability to diagnose xerosis until I read that comment. In an effort to recognize early changes of xerosis the authors studied 11 patients (6 women aged 26 to 82 years and 5 men aged 67 to 87 years) and found that in xerotic areas of any size, stage, and race, white scales were always detectable in dermoscopy, which was called white scale sign (WSS). The WSS was not apparent if alcohol was used prior to dermoscopy or once emollients were applied. They acknowledge that many patients are not aware that their skin is dry. They conclude by proposing “that clinicians look for the WSS in patients of all ages. The WSS can contribute to the detection and diagnosis of xeroderma and thus allow suitable treatment before asteatotic eczema develops.” (5).
If a patient is not aware of a disorder, and it is asymptomatic, is it a problem? The only diagnostic dilemma I ever faced diagnosing xerosis was differentiating it from ichthyosis vulgaris. I routinely use dermoscopy for pigmented lesions, other neoplasms, and for inflammatory dermatoses. I have no doubt that the WSS is accurate – I just don’t see myself searching to diagnose asymptomatic dry skin. While it is certainly reasonable to recommend moisturization for those with xerosis (especially in elderly patients who may be at risk of becoming symptomatic), I am willing to wager that there are many people like myself who prefer to take the Lennon-McCartney approach to wintertime xerosis and let it be. Nobody is going to convince me to moisturize my skin unless I have to.
1. Norman RA. Xerosis and pruritus in the elderly: recognition and management. Dermatol Ther 2003; 16: 254-9.
2. Patel N, et al. Acquired ichthyosis. J Am Acad Dermatol 2006; 55: 647-56.
3. Valentine J, et al. Incidence and risk of xerosis with targeted anticancer therapies. J Am Acad Dermatol 2015; 72: 656-67.
4. Biniek K, et al. Understanding age-induced alterations to the biomechanical barrier function of human stratum corneum. J Dermatol Sci 2015; 80: 94-101.
5. Klemmer A. White scale sign for xeroderma. JAMA Dermatol 2016. Published online December 14.
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