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Haired skin is a defining characteristic of mammals. However, some specialized skin regions, such as human palms, soles and ventral wrist, and mouse plantar foot, are entirely hairless. Using mouse plantar skin as a model system, we show that the endogenous secreted Wnt inhibitor DKK2 suppresses plantar hair follicle development and permits the formation of hairless skin. Plantar skin retains all of the mechanistic components needed for hair follicle development, as genetic deletion of Dkk2 permits formation of fully functional plantar hair follicles that give rise to external hair, contain sebaceous glands and a stem cell compartment, and undergo regenerative growth. In the absence of Dkk2, Wnt/β-catenin signaling activity is initially broadly elevated in embryonic plantar skin and gradually becomes patterned, mimicking follicular development in normally haired areas. These data provide a paradigm in which regionally restricted expression of a Wnt inhibitor underlies specification of hairless versus hairy skin.

Primary cutaneous malignancies are among the most commonly diagnosed types of cancer worldwide. We aimed to examine the incidence and 5‐year survival rates of all types of primary cutaneous malignancies in the Korean population. Data from the Korean Nationwide Cancer Registry from 1999 to 2019 were analyzed. The crude incidence rates, age‐standardized incidence rates, and 5‐year relative survival rates of each type of skin cancer were calculated. A total of 89 965 patients were diagnosed with primary cutaneous malignancies, which was a 7‐fold increase from 1999 to 2019. The age‐standardized incidence rates increased 3.4‐fold in basal cell carcinoma (3.7/100 000 person‐years), 2.0‐fold in squamous cell carcinoma (1.6/100 000 person‐years), 12.0‐fold in Bowen disease (1.2/100 000 person‐years), and 1.8‐fold in malignant melanoma (0.7/10 000 person‐years) in 2019. Average annual percentage changes in age‐standardized incidence rates were statistically significant in basal cell carcinoma (15.8%), Bowen disease (5.8%), squamous cell carcinoma (5.1%), malignant melanoma (1.2%), melanoma in situ (1.1%), dermatofibrosarcoma protuberans (1.2%), mycosis fungoides (0.5%), primary cutaneous CD30+ T‐cell proliferations (0.5%), adnexal and skin appendage carcinoma (0.4%), extramammary Paget's disease (0.2%), and Merkel cell carcinoma (0.2%). The 5‐year relative survival rates were the highest in basal cell carcinoma (103.3%), followed by dermatofibrosarcoma protuberans (99.7%) and mycosis fungoides (96.6%), and lowest in angiosarcoma (24.7%). The 5‐year relative survival rates steadily increased in extramammary Paget's disease (23.6%), cutaneous B‐cell lymphoma (21.3%), mycosis fungoides (20.2%), extranodal NK/T‐cell lymphoma, nasal type (18.1%), and malignant melanoma (16.1%) from 1996–2000 to 2015–2019. Most primary cutaneous malignancies have increased in incidence and survival rates in the Korean population, but to varying extents depending on the type of skin cancer. [ABSTRACT FROM AUTHOR]

Background: Photoprotection is crucial in preventing the development and progression of various skin diseases. However, patients with skin disease have limited awareness of photoprotection. We evaluated the knowledge and behavioral patterns of photoprotection among Koreans with skin diseases. Methods: A cross‐sectional study was conducted in 11 general hospitals across South Korea. The study population consisted of patients aged 19 years or older who visited dermatologic clinics for their skin diseases. A self‐administered questionnaire was used to collect patient demographics, knowledge of photoprotection, and photoprotective habits. Results: In this study, 1173 patients with skin cancer, hyperpigmentary disorders, hypopigmentary disorders, or other skin diseases participated. Females scored significantly higher in knowledge of photoprotection compared to males (mean score 8.4 vs. 7.8; p <.001), and younger patients (<50 years) scored higher than older patients (mean score 8.7 vs. 7.5; p <.001). Males also reported longer sun exposure times and lower usage of photoprotective measures (both p <.001). Patients with skin cancer had the lowest mean knowledge score (7.1 ± 2.6) and were less likely to use photoprotective measures compared to other groups (p <.001). In contrast, patients with hyperpigmentation actively avoided sun exposure compared with other groups (p < 0.001). Conclusions: Knowledge of photoprotection among Korean patients with skin diseases varied depending on the gender, age, and type of skin disease. Their photoprotective behaviors were inadequate, especially among males and those with skin cancer. These findings emphasize the importance of educating and tailoring photoprotection strategies for patients with skin diseases. [ABSTRACT FROM AUTHOR]

The authors are indebted to all the individuals who took part in these studies and all the researchers who enabled this work to be carried out. Patients with hair loss need to be made aware that dermatologists are more adept at treating hair disorders such as alopecia based on accurate diagnosis, than other physicians. Furthermore, if patients delay treatment for systemic problems such as lupus or alopecia neoplastic, hair loss may be irreversible.1,3,10 Thus, dermatologists should focus their efforts on informing the public that hair loss is a dermatologic disorder, so that patients with alopecia can consult a dermatologist before receiving other inappropriate diagnoses and treatments. [Extracted from the article]