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Generalized pustular psoriasis (GPP) is a rare inflammatory skin disease that can be life-threatening. Recently, it has been reported that familial GPP is caused by homozygous or compound heterozygous mutations of IL36RN. However, the majority of GPP cases are sporadic and it is controversial whether IL36RN mutations are a causative/predisposing factor for sporadic GPP. We searched for IL36RN mutations in two groups of GPP patients in the Japanese population in this study: GPP without psoriasis vulgaris (PV), and GPP with PV. Eleven cases of GPP without PV (GPP alone) and 20 cases of GPP accompanied by PV (GPP with PV) were analyzed. Surprisingly, 9 out of 11 cases of GPP alone had homozygous or compound heterozygous mutations in IL36RN. In contrast, only 2 of 20 cases of GPP with PV had compound heterozygous mutations in IL36RN. The two cases of GPP with PV who had compound heterozygous mutations in IL36RN are siblings, and both cases had PV-susceptible HLA-A*0206. We determined that GPP alone is a distinct subtype of GPP and is etiologically distinguished from GPP with PV, and that the majority of GPP alone is caused by deficiency of the interleukin-36 receptor antagonist due to IL36RN mutations.

Dermatoscopy is a non-invasive and cost-efficient imaging technique augmenting clinical examination in neoplastic and non-neoplastic dermatoses. Recently, novel dermatoscopic techniques based on principles of reflectance/absorption and excited fluorescence have been developed. However, comprehensive data on their applications are sparse, and terminology is inconsistent. In this systematic review, we addressed the principles of ultraviolet (UV) imaging and proposed categorization based on spectral characteristics and signal acquisition, as well as discussed documented and potential clinical applications, safety measures during examination, and limitations associated with reflectance and fluorescence dermatoscopy. A literature search was conducted in the PubMed medical database until 2 December 2023 according to PRISMA guidelines, and 28 papers fit the scope of this review, whereas additional relevant articles were included to provide broader context regarding the chosen terminology, chromophores described, safety of sub-UV/UV, and regulations for light-emitting devices. UV and sub-UV dermatoscopy, categorized into different methods on the basis of the emitted wavelength and signal acquisition process (reflectance versus fluorescence), augment conventional dermatoscopy by optimizing safety margins in melanoma, facilitating early detection of tumor recurrence, and enhancing visualization in non-neoplastic conditions, including pigmentation disorders, intertrigo, papulo-desquamative dermatoses, and beyond. The review highlights the limitations of these techniques, including difficulty in differentiating melanin from hemoglobin, challenges in evaluating uneven surfaces, and artifacts. Although UV dermatoscopy complements conventional dermatoscopy, clinicians should be aware of their peculiarities, artifacts, limitations, and safety concerns to optimize their diagnostic accuracy and ensure patient’s safety.

Extramammary Paget disease (EMPD) is a rare skin cancer that typically occurs in the anogenital area of older people. Since efficacy of treatments for metastatic or unresectable EMPD remains poor, development of a novel therapeutic approach is strongly desired. However, the lack of EMPD models has hampered investigation of EMPD. Here we investigated whether trophoblast cell surface antigen 2 (TROP2) could be a promising therapeutic target for EMPD. We retrospectively collected 108 samples from 54 patients with primary and metastatic EMPD from 10 Japanese institutions, and compared TROP2 expression between primary and metastatic lesions of each paired sample. In vitro assays were performed using a newly established EMPD cell line, KS-EMPD-1. TROP2 was strongly and homogeneously expressed in patient tissues, regardless of primary or metastatic lesions. The KS-EMPD-1 cells were treated with a TROP2-targeted antibody–drug conjugate (ADC), sacituzumab govitecan, and it significantly reduced cell viability in a dose-dependent manner compared with that of the cells treated with sacituzumab alone. Knockdown of TROP2 reduced cell viability and cell migration, and caused slight upregulation of the apoptosis-related factors, together with downregulation of the epithelial-to-mesenchymal transition-related factors. These findings suggest that a TROP2-targeted ADC may be a promising treatment option for unresectable EMPD.

Background Light absorption by melanin is greater in the ultraviolet spectrum than in the visible light spectrum. Purple light in the near‐ultraviolet–visible region (380–430 nm) also corresponds to a highly absorptive wavelength of melanin. Therefore, images captured under purple light are remarkably suited to detect subtle alterations in skin pigment contents. Objectives We compared two prototype dermoscopy cameras (DZ‐D100; Casio Computer Co., Ltd.): one with a 385 nm light (P385) and the other with a 405 nm light (P405), to clarify which wavelength could more clearly show dermoscopic structures. Methods Sixteen Japanese patients with 19 lesions, who visited our department were photographed with the P385 and P405 cameras under the same conditions. We evaluated the visual perception of lines, dots/clods, lesion borders and background around the lesion, as well as exposure, including appropriate brightness and underexposure, using the scores. Results Underexposure was significantly less in the P385 image than in the P405 image (p < 0.0001), while lines (p < 0.01) and lesion borders (p < 0.05) were significantly more distinct. Furthermore, visual perception of lines (p < 0.01) and lesion borders (p < 0.05) were significantly better in the P385 images. However, other visual perception items showed no significant differences between the two images. One exception was with the dermoscopy of melanocytic naevus in a patient with albinism, where the lines and dots/clods were clear in the P405 image but blurred in the P385 image. Conclusions When used as a complement to conventional dermoscopy images, the P385 images are thought to be less underexposed and easier to use in diagnosing lesions in slightly pigmented skin types, including in the Japanese who were the participants of this study. Meanwhile, the P405 images are potentially useful in the evaluation of light skin‐type lesions. Two dermoscopy cameras (p385 and p405) with prototype 385 nm and 405 nm violet wavelengths were used to observe which one clearly showed subtle changes in skin pigmentation and dermoscopic structure. The p385 images were significantly less underexposed than the p405 images, and the lines and lesion borders were significantly clearer. p385 images may be useful in diagnosing lesions in slightly pigmented skin types, while p405 images may be useful in evaluating lesions in lighter skin types.

Background In clinical practice, the quality of images may vary depending on the imaging device, and the focus of the dermoscope is on the superficial layer of the lesion. Therefore, it is desirable to have a dermoscopy device that can easily focus on any lesion and clearly show the findings. Objectives We conducted a clinical study to compare dermoscopic images of the same skin tumours obtained using a prototype dermoscopy camera, DZ‐D100 (DD, Casio Computer Co., Ltd.), and three existing dermoscopy imaging devices (Derma9500S®‐GR or DG, Derma Medical Inc.; DELTA 20® T or DT, HEINE Optotechnik; and DermLite Foto II Pro® or DF, DermLite LLC). Methods Dermoscopic images of 117 skin tumours from 94 patients who visited Chiba University Hospital were evaluated by two experts in terms of the focus, and the clarity and presence or absence (the primary endpoint) of seven findings (pigmented lines, shiny white lines, dots/globules, blue‐grey structures, vascular structures, milia‐like cysts and comedo‐like openings). Results No significant differences in the number of cases with each of the seven findings (pigmented lines, shiny white lines, dots/globules, blue‐grey structures, vascular structures, milia‐like cysts and comedo‐like openings) among the four groups were observed. The clarity of focus was significantly better with the DD than with the other three devices (all, p < 0.05). Pigmented lines were significantly clearer with the DD than with the DF and DT (all, p < 0.05). A strong correlation was found between the focus and clarity of pigmented lines/globules, blue‐grey structures and vascular structures (all, p < 0.005). Conclusions DD was less affected by elevated lesions and was considered to be the easiest to focus and recognize brown to black lines and dots/globules. The well‐focused captured images are also expected to be applied to diagnosis by artificial intelligence.

Intravascular large B-cell lymphoma (IVLBCL) is a rare type of extranodal, diffuse, large B-cell lymphoma characterized by the selective growth of lymphoma cells within the lumen of small blood vessels, with no lymphadenopathy or masses. Herein, we report a cutaneous variant of IVLBCL that is rare in Asia. A healthy 73-year-old Japanese woman presented to our hospital with painful erythematous indurations and telangiectasia of the lower extremities, which was confirmed on dermoscopy. Physical examination revealed no systemic involvement, and laboratory parameters were within normal ranges. No abnormal FDG uptake was detected on 18FDG-PET/CT. Histopathological examination revealed proliferation and dilatation of blood vessels in the subcutis layer, occluded by CD20-positive atypical lymphoid cells. Thus, the patient was diagnosed with a cutaneous variant of IVLBCL without systemic symptoms. In conclusion, it is important to confirm telangiectasia using dermoscopy and perform skin biopsies in patients presenting with sudden-onset erythematous induration.

A 73-year-old Japanese male patient presented to our hospital with a red nodule arising from the lower abdomen to the base of the penis. After the biopsy, the tumor was diagnosed as sweat gland carcinoma with neuroendocrine differentiation (SCAND) with bilateral inguinal lymph node metastasis. SCAND is newly proposed entity and very rare disease in 2022. Although SCAND often showed stromal mucin deposition, a tumor mass floating in abundant mucus, which was never reported before in SCAND, was observed histopathologically in our case. Primary cutaneous mucinous carcinoma (PCMC) with neuroendocrine differentiation was considered as a differential diagnosis. However, the feature only occupied a small portion of the tumor (<10%), and PCMC predominantly originated in the head and neck region. Therefore, we considered PCMC could be ruled out. Consequently, while SACND and PCMC sometimes share histologic similarities, their differentiation is important because PCMC rarely metastasizes while SCAND often does.

Soluble CD14 (sCD14) is one of the immunomodulatory factors in breast milk (BM). Although it may be involved in the prevention of atopic symptoms and sensitization to both food and inhalant allergens, conflicting evidence exists concerning its protective effects. In this study, we investigated the relationship between sCD14 in colostrum and 1-month BM, and the development of atopic dermatitis (AD) and sensitization to food and aeroallergens at 9 months of age in infants who were exclusively or almost exclusively breastfed up to 4 months of age. BM samples were collected from lactating mothers who participated in a 2 × 2 factorial, randomized, nontreatment controlled trial study set in Tokyo, which looked at the efficacy of emollients and synbiotics in preventing AD and food allergy in children during the first year of life. A total of 258 colostrum samples and 269 1-month BM samples were analyzed. We found that one-month BM sCD14 levels in the AD group were significantly lower than in the non-AD group. Levels of sCD14 in 1-month BM were not related to allergen sensitization in the overall analysis, but egg white sensitization correlated inversely with 1-month BM sCD14 in infants without AD. The results suggest that sCD14 in BM may be involved in atopic manifestations in early infancy.

We aimed to elucidate the dermoscopic vasculature of patients with Bowen Disease (BD) that was misdiagnosed as chronic eczema and had branched and/or reticular vessels after topical steroid application. The medical records of 19 patients with BD on the upper trunk were retrospectively reviewed for steroid use history, vascular structure observed in dermoscopy, and corresponding histological findings. Four patients treated with strong topical steroids showed remarkable branched and/or reticular vessels on dermoscopy. Histopathology showed partial epidermal atrophy with irregular thin elongation of the rete ridges, atypical keratinocyte proliferation in the epidermis, and vasodilation in the superficial dermis. We considered that vasodilation and partial epidermal atrophy may be induced by topical steroid application in BD-affected areas. In cases of suspected BD with reddish-brown plaque showing branched and/or reticulated vessels in dermoscopy, confirming a history of topical steroid use is helpful.

Background Few studies have examined the effectiveness of the reciprocity law in ultraviolet excimer therapy. This study aimed to examine the difference in erythematous reaction in human skin when the irradiance of ultraviolet excimer treatment devices differed while the irradiation dose was constant. Materials and methods This study, conducted at the Department of Dermatology, Chiba University, included 15 healthy adults aged 20–65 years (mean age, 46.3 years; seven men). Using ultraviolet excimer treatment devices with different irradiances (50 or 150 mW/cm2), the upper abdomen of each participant was irradiated with ultraviolet light at set irradiation doses (80, 100, 120, 140, 160, 180, and 200 mJ/cm2). The erythema index of each irradiated site was measured using a melanin‐ and erythema‐measuring device, and the difference in erythema index before and 24 h after irradiation was the primary endpoint. Results The change in erythema index was significantly higher for an irradiance of 150 mW/cm2. Significant differences (p < 0.05) were observed between these irradiance levels at irradiation doses of 100‒200 mJ/cm2. Conclusions Even for the same irradiation dose, stronger erythematous reactions occurred at higher irradiances in ultraviolet excimer treatment. This suggests that the reciprocity law may not always hold true in excimer therapy.