Review articleAlopecia areata: What’s new in epidemiology, pathogenesis, diagnosis, and therapeutic options?
Section snippets
Incidence
The lifetime incidence risk of alopecia areata (AA) was estimated to be 2.1% in Olmsted county, Minnesota, for 20 years (1990–2009) [1]. The age- and sex-adjusted incidence was 20.9 per 100,000 person-years. The number of female patients was 51% and the median age at diagnosis was 33 years. These results were similar to those in the same county from 1975 to 1989, and the incidence of psoriasis from 1982 to 1991 was 700.9 per 100,000 person-years [2]. Among 1761 patients with newly diagnosed AA
Genetics
Biran et al. published a review on the genetics of AA in the April 2015 issue of this journal and detailed information on the connection to pathogenesis is available [23]. We here pick up the most outstanding works in this research field since 2010 .
In 2010, Petukhova et al. identified 139 single nucleotide polymorphisms (SNPs) related to AA in six chromosomal regions in GWAS in 1024 AA patients and 3278 controls, and found that ULBP3 is a novel AA gene [24]. ULBP3 encodes a natural killer
Dermoscopy/trichoscopy
Dermoscopy has been applied for the scalp for the diagnosis of hair disorder. It is also called “trichoscopy” whereas the term may be used for the microscopy of hair.
There have been 90 papers on dermoscopy in AA since 2010 whereas there were only 14 papers before 2009, corresponding with the increase in the use of the dermoscopy technique in the diagnosis of AA. Characteristic signs of AA in dermoscopy include yellow dots, black dots, tapering hair, broken hair, and short vellus hair. Some
Evidence for current treatments (Table 4)
In 2012, British Association of Dermatologists updated the 2003 guidelines for the management of AA [81]. The following two treatments were recommended with a strength of recommendation C (a body of evidence in high-quality systematic reviews of case-control or cohort studies, or high-quality case-control or cohort studies): potent topical steroid and intralesional corticosteroid for limited patchy hair loss; and contact immunotherapy for extensive patchy hair loss and alopecia
JAK inhibitors
Janus kinase (JAK) is a receptor tyrosine kinase regulating a number of cytokine receptor signaling pathways and its inhibitors have been applied for the treatment of several chronic inflammatory diseases. Clinical studies have shown its efficacy on inflammatory skin disorders, such as psoriasis [117] and atopic dermatitis [118]. JAK inhibitors are expected to suppress the inflammatory spirals not only by the direct effect on immune cells, but also by the improvement of the skin barrier in
Concluding remarks
We identified the three most important scientific questions to be answered in the next 10 years and the missions required to obtain these answers:
- 1)
What is the identity, details, and activation mechanisms of the effectors NKG2D+CD8+ cells [24]? Are they a unique and independent subset? If AA partly simulates the actual protective response against infections and dangers [140], what is the original target of NKG2D+CD8+ cells? Which receptors do they utilize? Do commensal microorganisms trigger the
Teruki Dainichi is a Junior Associate Professor at the Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan from 2013. He received the MD in 1996 and PhD in 2001 from Tokushima University Faculty of Medicine, Tokushima, Japan. He was assigned as a Staff Dermatologist (2001–2005) and an Assistant Professor (2005–2007) at the Department of Dermatology, Kyushu University Hospital, Fukuoka, Japan. He was assigned as an Assistant Professor at the Department of
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Teruki Dainichi is a Junior Associate Professor at the Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan from 2013. He received the MD in 1996 and PhD in 2001 from Tokushima University Faculty of Medicine, Tokushima, Japan. He was assigned as a Staff Dermatologist (2001–2005) and an Assistant Professor (2005–2007) at the Department of Dermatology, Kyushu University Hospital, Fukuoka, Japan. He was assigned as an Assistant Professor at the Department of Dermatology, Kurume University, Kurume, Japan (2007–2012), a Postdoctoral Research Scientist (2009–2011) and Associate Research Scientist (2012) at the Department of Microbiology and Immunology, Columbia University, New York. His current clinical specialty is bullous diseases and alopecia and his research interests are keratinocyte biology and immunology of the skin.