[MACULOPAPULAR CUTANEOUS MASTOCYTOSIS HARBORING A KIT MUTATION (ASP419DEL): A CASE REPORT].

A 2-year-old, male patient presented with an 18-month history of scattered, brown macules and nodules up to 2 cm in size on his trunk and extremities. These macules were accompanied by pruritus and were positive for Darier's sign. A skin biopsy of a brown macule on the left thigh revealed a dense accumulation of CD117-positive, round or oval cells with amphophilic cytoplasm within the upper to middle dermis. The patient was otherwise healthy and had normal laboratory and imaging test results. Sequence analysis of genomic DNA from a skin biopsy demonstrated the presence of an Asp419del mutation in exon 8 of the KIT gene. Based on these findings, maculopapular cutaneous mastocytosis (MPCM) was diagnosed. The patient received H 1-antihistamine. Although the pruritus resolved, the brown macules remained for one year after the initial treatment. To the best of our knowledge, only three cases of cutaneous mastocytosis (CM) with an Asp419del mutation, including the present case, have been reported in the Japanese literature to date; moreover, while the previous two cases were of DCM, the present case was the first instance of MPCM. Normally, the symptoms of childhood-onset MPCM are dormant until puberty. However, a recent study reported that many MPCM patients may experience persistent or exacerbated symptoms. The present study therefore evaluated 53 Japanese cases of childhood onset MPCM with a KIT gene mutation and discussed the patients' clinical outcomes.

Topical application of imatinib mesylate suppresses vitamin D3 analog-induced dermatitis in Balb/c mice.

Atopic dermatitis (AD) is an allergic disease mediated by Th2 cells. In AD, externally stimulated keratinocytes release inflammatory cytokines, such as IL-33 and TSLP. Inflammatory cells infiltrate skin tissue and increase vascular permeability. Therefore, we hypothesized that imatinib mesylate (IMT), which suppresses vascular permeability, may be a candidate therapeutic agent for AD. A vitamin D3 analog (MC903) was administered daily to both ears of Balb/c mice to create a murine AD model to which IMT was applied. The skin lesions were evaluated histopathologically and by immunostaining. Cytokine expression in the skin was assessed by using real-time polymerase chain reaction (PCR) and immunostaining and was investigated using Evans Blue to determine whether IMT suppressed vascular permeability due to histamine. The suppressive effect of TNF-α/IL-4-induced TSLP expression in primary mouse keratinocytes (MKCs) treated with IMT was then investigated. Tslp gene and protein expression in the lesion was measured using real-time PCR and ELISA. The activation of signal transduction was analysed by western blotting. Topical application of IMT significantly reduced ear thickness, Evans blue leakage, and scratch onset. IMT suppressed the number of infiltrating cells (CD4+ T cells, eosinophils, and basophils), and the expression of IL-13, IL-33, and TSLP in a MC903-induced, murine AD model and inhibited TNF-α/IL-4-induced TSLP expression via downregulation of ERK phosphorylation in MKCs. IMT reduced the skin symptoms in a MC903-induced, murine AD model, suggesting that it may have potential as a new treatment for AD.

[ANALYSIS OF 201 PATIENTS WITH ATOPIC DERMATITIS RECEIVING DUPILUMAB AT TOKYO MEDICAL UNIVERSITY HOSPITAL].

OBJECTIVE: The present study aimed to assess the course of patients with atopic dermatitis (AD) receiving dupilumab treatment. METHODS: The present, retrospective survey enrolled 201 patients with AD between May 2018 and May 2022 to examine their previous treatment, skin score, percentage of self-injections, EASI improvement rate, treatment continuation rate, number of treatment interruptions, and reasons for the interruptions. RESULTS: The average EASI severity score was 39.5±18.1, and the self-injection rate was 83%. The percentage of improvement in patients with an EASI-75 was 63% at week 16 and EASI 100 was 15.9% at week 60. At week 16 of treatment, the patients were divided by their improvement rate into an EASI-75, < 50 group. The EASI-75 group maintained their improvement rate until week 60. In the EASI< 50% group achieved 73.4% at week 60. The treatment continuation rate was 82.6%, and 35 patients discontinued the treatment, in most cases shortly after commencement. CONCLUSION: Dupilumab has revolutionized AD treatment, markedly improving skin symptoms. The present study was the first in Japan to demonstrate a treatment continuation rate of 82.6% at week 60 at a single center. Clear guidelines on long-term, complete maintenance treatment with dupilumab await formulation.

IL-25 contributes to development of chronic contact dermatitis in C57BL/6 mice, but not BALB/c mice.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by type 2 immune responses. Interleukin-25 (IL-25) is produced predominantly by epithelial cells. It can activate Th2 cells to produce type 2 cytokines such as IL-4, IL-5 and IL-13, contributing to host defense against nematodes. However, excessive/inappropriate production of IL-25 is considered to be involved in development of type 2 cytokine-associated allergic disorders such as asthma. On the other hand, the contribution of IL-25 to the pathogenesis of AD remains poorly understood. In the present study, we found that expression of Il25 mRNA was significantly increased in the skin of mice during oxazolone-induced chronic contact hypersensitivity (CHS), which is a mouse model of human AD. In addition, development of oxazolone-induced chronic CHS was significantly reduced in IL-25-deficient (Il25-/-) mice compared with wild-type mice on the C57BL/6, but not BALB/c, background, although IL-25 was not essential for IL-4 production by hapten-specific T cells. Therefore, IL-25 is crucial for development of chronic CHS, although that is partly dependent on the genetic background of the mice.

[A CHILD CASE OF DIFFUSE CUTANEOUS MASTOCYTOSIS].

Cutaneous mastocytosis (CM) usually appears in childhood and improves substantially before adolescence. The c-KIT mutation of D816V is present in 36% and 20% of patients with childhood-onset CM and diffuse cutaneous mastocytosis (DCM), respectively. In some cases of childhood-onset DCM, the disease can progress to systemic mastocytosis; in others, it resolves spontaneously. Thus, assessing the prognosis is difficult. Herein, we described a case of DCM in an 11-month-old, male patient without a c-KIT mutation. The patient presented with dark brown macules and sporadic erythema topped by bullous lesions. A skin biopsy of the macule on the abdomen revealed accumulation of mast cells which were round to oval-shaped with amphophilic cytoplasm within the upper dermis. The patient had received H1 inhibitor until age 3 years and continued to experience blisters on the trunk. However, no severe symptoms, such as anaphylaxis, occurred. Included in this manuscript is a review of previous reports of childhood-onset DCM in Japan and cases specifically seen at our dermatology clinic.

IL-25 enhances TH17 cell-mediated contact dermatitis by promoting IL-1ß production by dermal dendritic cells.

BACKGROUND: In addition to thymic stromal lymphopoietin and IL-33, IL-25 is known to induce TH2 cytokine production by various cell types, including TH2 cells, TH9 cells, invariant natural killer T cells, and group 2 innate lymphoid cells, involved in TH2-type immune responses. Because both TH2-type and TH17-type cells/cytokines are crucial for contact hypersensitivity (CHS), IL-25 can contribute to this by enhancing TH2-type immune responses. However, the precise role of IL-25 in the pathogenesis of fluorescein isothiocyanate-induced CHS is poorly understood. OBJECTIVE: We investigated the contribution of IL-25 to CHS using Il25-/- mice. METHODS: CHS was evaluated by means of measurement of ear skin thickness in mice after fluorescein isothiocyanate painting. Skin dendritic cell (DC) migration, hapten-specific TH cell differentiation, and detection of IL-1ß-producing cells were determined by using flow cytometry, ELISA, and immunohistochemistry, respectively. RESULTS: In contrast to thymic stromal lymphopoietin, we found that IL-25 was not essential for skin DC migration or hapten-specific TH cell differentiation in the sensitization phase of CHS. Unexpectedly, mast cell- and non-immune cell-derived IL-25 was important for hapten-specific TH17 cell-mediated rather than TH2 cell-mediated inflammation in the elicitation phase of CHS by enhancing TH17-related, but not TH2-related, cytokines in the skin. In particular, IL-1ß produced by dermal DCs in response to IL-25 was crucial for hapten-specific TH17 cell activation, contributing to induction of local inflammation in the elicitation phase of CHS. CONCLUSION: Our results identify a novel IL-25 inflammatory pathway involved in induction of TH17 cell-mediated, but not TH2 cell-mediated, CHS. IL-25 neutralization can be a potential approach for treatment of CHS.

IL-36α is involved in hapten-specific T-cell induction, but not local inflammation, during contact hypersensitivity.

Levels of IL36α are known to be increased in specimens from patients with atopic dermatitis and psoriasis. In addition, it has been reported that IL-36α is crucial for development of imiquimod-induced psoriatic dermatitis in mice. On the other hand, the role of IL-36α in induction of allergic contact dermatitis/contact hypersensitivity (ACD/CHS) is poorly understood. We found that IL-36α was produced in keratinocytes of mice during imiquimod-induced psoriatic dermatitis, but it was hardly detectable in the skin of mice during either fluorescein isothiocyanate (FITC)- or 1-fluoro-2, 4-dinitrobenzene (DNFB)-induced CHS. Although IL-36α can enhance activation of dendritic cells (DCs) and T cells, in CHS, IL-36α was not essential for DC migration from the skin to draining LNs, but it was required for induction or activation of hapten-specific T cells such as Th/Tc1 or Th17 cells. However, local inflammation, assessed by measurement of ear skin thickness, was comparable between wild-type and IL-36α-deficient mice during both FITC- and DNFB-induced CHS. These observations indicate that IL-36α is involved in induction and/or activation of hapten-specific T-cell subsets in the sensitization phase of CHS, but not essential for induction of local inflammation in the elicitation phase.

A pulmonary metastatic model of murine melanoma assessed by magnetic resonance imaging.

Immune checkpoint inhibitors and kinase inhibitors have improved prognosis of malignant melanoma (MM) patients. However, these therapies cannot completely overcome the metastasis of MM. Thus, development of new therapy against metastasis should be required. A first step towards this goal, the aim of this study, is to establish a model of pulmonary metastasis from primary cutaneous MM and a monitoring system. B16-F10, a murine melanoma cell line, was subcutaneously injected into the pinna of mice. The pinna was excised when the lesion was detected. A metastatic nodule on T2-weighted imaging was detected 4 weeks after resection of the pinna. Lung metastases were observed in 37.5% (6/16) of the specimens. We established a novel murine model of the high pulmonary metastasis of MM. The MRI was useful for observations of the growth of the metastatic lesions in the lungs without dissection.

IL-33 promotes ICAM-1 expression via NF-kB in murine mast cells.

BACKGROUND: IL-33, a member of the IL-1 cytokine family, binds to heterodimeric receptors ST2 and IL-1 receptor accessory protein, and activates Th2-type immune responses. The signals from the ST2 receptor are mediated by the two major pathways, including AP-1 and NF-κB molecules. The present study examined whether IL-33 induced ICAM-1 expression in bone marrow-derived mast cells (BMMCs). METHODS: BMMCs from C57BL/6J mice, cultured in media containing IL-3 (20 ng/ml), were treated with IL-33 (50 ng/ml) for up to 72 h. ICAM-1 expression with mRNA and protein, degranulation of siRNA ICAM-1 transfected BMMCs, and cell adhesion were analyzed. In the in vivo part of the experiment rIL-33 (500 ng) was injected intradermally into the ear pinnae of mice and any resulting pathological changes were assessed. RESULTS: ICAM-1 mRNA expression was increased one hour after IL-33 stimulation while ICAM-1 protein attained maximum expression levels 24 h after IL-33 stimulation. Moreover, IL-33-treated BMMCs showed increased cell adhesion to the LFA-1-coated plate. However, siRNA ICAM-1 transfected BMMCs did not affect Ag/IgE-mediated degranulation level compared to the wild control siRNA. Pre-treatment with a NF-κB inhibitor dramatically reduced ICAM-1 expression in IL-33-treated BMMCs, suggesting the involvement of NF-κB in the process. In vivo study, at 6 h after IL-33 treatment, MCs histologically showed up-regulated ICAM-1 expression though the number of tryptase-positive cells did not change. CONCLUSIONS: These data suggest that MCs increase ICAM-1 expression and activate LFA-1 positive cells in the early phase of skin inflammation in response to IL-33.

Roles of Mast Cells in Cutaneous Diseases.

Mast cells are present in all vascularized tissues of the body. They are especially abundant in tissues that are in frequent contact with the surrounding environment and act as potential sources of inflammatory and/or regulatory mediators during development of various infections and diseases. Mature mast cells' cytoplasm contains numerous granules that store a variety of chemical mediators, cytokines, proteoglycans, and proteases. Mast cells are activated via various cell surface receptors, including FcϵRI, toll-like receptors (TLR), Mas-related G-protein-coupled receptor X2 (MRGPRX2), and cytokine receptors. IgE-mediated mast cell activation results in release of histamine and other contents of their granules into the extracellular environment, contributing to host defense against pathogens. TLRs, play a crucial role in host defense against various types of pathogens by recognizing pathogen-associated molecular patterns. On the other hand, excessive/inappropriate mast cell activation can cause various disorders. Here, we review the published literature regarding the known and potential inflammatory and regulatory roles of mast cells in cutaneous inflammation, including atopic dermatitis, psoriasis, and contact dermatitis GVHD, as well as in host defense against pathogens.