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Infective dermatitis associated with human T-cell lymphotropic virus type-1 (HTLV-1) (IDH) is a severe form of chronically infected eczema occurring in early childhood, although very rarely cases have been reported in adults. Most of the cases are from Jamaica and Brazil and occur in individuals with low socioeconomic status. IDH is always associated with refractory Staphylococcus aureus or beta-hemolytic Streptococcus infection of the skin and nasal vestibules. Patients with IDH may develop other even more severe HTLV-1-associated diseases, such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) of early or late appearance and adult T-cell leukemia/lymphoma. In the context of the Brazilian experience, it has been observed that 54% of IDH patients exhibit the juvenile form of HAM/TSP while the estimated incidence of adult HAM/TSP is 3%. As there are no curative treatments for HTLV-1 infection (or vaccines) or most of its associated diseases, prevention of infection is fundamental, mainly by vertical transmission, as it is responsible for the development of IDH, infantojuvenile HAM/TSP, and ATL. Public measures to reduce this transmission must be implemented urgently. Furthermore, it is recommended, mainly in HTLV-1 endemic areas, to search for HTLV-1 infection in all patients with infected eczema, even in adults., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease predominantly affecting synovial joints. Extra-articular manifestations, including skin involvement, can also occur. The most frequent cutaneous manifestation in RA patients is rheumatoid nodules, occurring in 20-30% of seropositive individuals. These nodules are typically firm, painless, and located on pressure points such as the hands and elbows. However, in a minority of cases, other skin conditions can complicate RA, notably palisaded neutrophilic granulomatous dermatitis (PNGD). PNGD presents as erythematous papules or plaques, often pruritic and distributed symmetrically over extensor surfaces, making it challenging to differentiate from rheumatoid nodules. Histopathological examination is crucial to establish the diagnosis. High clinical suspicion and appropriate referral to Dermatology are essential for accurate diagnosis and management. Treatment of PNGD is focused on underlying disease control. Other options include topical, intralesional or systemic corticosteroids, dapsone or hydroxychloroquine. Herein, we present the case of a 71-year-old woman with RA who developed PNGD, highlighting the importance of a multidisciplinary approach for achieving a favorable clinical outcome.

Cutaneous granulomatous reactions are diverse, both from the clinical and the pathological perspective. Most underlying pathophysiological aspects remain elusive. Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis have been claimed to be reactions to systemic disorders, such as infectious, inflammatory, or neoplastic conditions. Recently, the overarching term "reactive granulomatous dermatitis" has been coined to unify both entities. We herein report two cases of reactive granulomatous dermatitis presenting with the widely known, albeit infrequent "rope sign" and provide clinicopathological correlation. The two patients included a 53-year-old woman with enlarging erythematous plaques and underlying palpable cords on both sides of trunk near axillae (rope sign), and a 51-year-old woman with personal history of rheumatoid arthritis and a palpable cord on the left aspect of the trunk. Pathological findings were compatible with reactive granulomatous dermatitis in both cases. In conclusion, the rope sign represents a strikingly infrequent but decisive diagnostic clue of reactive granulomatous dermatitis.

Superficial granulomatous pyoderma gangrenosum is a rare, superficial, vegetating form of pyoderma gangrenosum that tends to occur as a single lesion, most commonly on the trunk. Herein, we report a clinically confounding case of disseminated superficial granulomatous pyoderma gangrenosum in a patient with a 5-year history of painful and chronic ulcerations of the bilateral upper extremities and face in a sun exposed distribution. This was a diagnostically challenging case due to the treatment-refractory nature of our patient's skin lesions and the atypical clinical and histologic presentations encountered. We review our clinical decision process and acknowledge other entities that were considered during the clinical course of this case. Additionally, we discuss the lack of responsiveness to various treatment options with eventual successful clearance of this patient's active skin disease with initiation of adalimumab.

A 5-y-old, Piedmontese cow had a 4-mo history of ongoing development of skin masses. This was the only cow affected in a herd of 20 cows. Up to 12, hairless, red-to-black, raised nodules-to-plaques were distributed along the dorsum and tail head. Biopsies were taken for histopathology and ancillary testing. An ulcerated skin section contained dermal infiltrates of eosinophils, plasma cells, neutrophils, macrophages, lymphocytes, and multinucleate giant cells, and pyogranulomas. Fungal hyphae were seen within the dermis, multinucleate giant cells, and pyogranulomas. In pyogranulomas, fungi were surrounded by a Splendore-Hoeppli reaction. Dematiaceous (pigmented) hyphae were rarely observed with H&E-stained and unstained (cleared and mounted) sections, but stained well with a Fontana-Masson stain. Exserohilum mcginnisii was identified by fungal culture, followed by PCR assay and sequencing. Exserohilum is a dematiaceous fungus that causes disease in humans and rarely in animals. The use of unstained sections and Fontana-Masson stain are important to demonstrate pigment because dematiaceous fungi have little melanin and appear as hyaline hyphae histologically. PCR assay and sequencing aid in the differentiation and classification of fungal species. To our knowledge, E. mcginnisii dermal granulomas have not been reported previously in cattle., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Pattern analysis of inflammatory skin diseases is a technique that offers a systematic approach to the histologic diagnosis of skin diseases. First introduced to human dermatopathology in the 1970s, it was widely adopted by veterinary pathologists for the histologic diagnosis of skin diseases in animals. As the inflammatory pattern reflects, to varying extents, aspects of the underlying disease pathogenesis, its use has contributed to the recognition of novel skin diseases in domestic animals, particularly in dogs and cats. Alternative diagnostic approaches used in human dermatopathology, such as "tissue-reaction pattern" and a purely "anatomic approach" have not been as widely used in veterinary pathology. However, veterinary pathologists often combine pattern analysis with anatomic and etiologic factors. This overview outlines the technique, introduces the patterns, and discusses advantages and limitations of pattern analysis in veterinary diagnostic dermatopathology. While molecular analytic techniques and image informatics will undoubtedly prove to be revolutionary in many areas of diagnostic pathology, it is recognized in both human and veterinary arenas that the light microscopic interpretation of hematoxylin and eosin-stained tissue sections will remain the mainstay of routine dermatopathology diagnosis for the foreseeable future., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Pigmented purpuric lichenoid dermatitis (PPLD) is a rare subtype of pigmented purpuric dermatosis, which classically presents with a mixture of lichenoid papules and patches on the bilateral lower extremities. Herein, we describe an unusual case of a 47-year-old man with PPLD who presented with 1-3mm discrete papules without the presence of larger patches. The diagnosis of PPLD should be considered for patients presenting with bilateral symmetric discrete papules on the legs.

Introduction: Equine pastern dermatitis has a high prevalence in the equine population, especially in draft breeds. This skin condition is difficult to treat, and it is suspected that owners often decide on a treatment without consulting a veterinarian. The objectives of this study were to describe owner-reported clinical signs, severity, and reasons to consult a veterinarian. Moreover, we inquired about preventive measures and treatments, both instituted by owners without previous consultation or prescribed by their veterinarians. A total of 123 horses (owners recruited over social media) were included in the study. All horses suffered from equine pastern dermatitis at least once in the two years preceding the study. Standardized questionnaires collecting information on management, housing conditions, clinical signs as well as preventive measures and treatments were filled out by participants. The data was recorded, and descriptive statistics were performed. Most horses (71 out of 115 available answers, 62 %) had shown clinical signs of equine pastern dermatitis at least four times in their lives. A total of 113 horses (92 % of all included horses) were affected by equine pastern dermatitis at the time of the interview. For 37 horses (32 %) out of 114 available answers the owners consulted their veterinarian only after the horse showed signs of pain or lameness. Usually, treatments that did not require a medical prescription were applied without consulting their veterinarian (e. g. only 9 % (14 out of 150 prescriptions) of topical creams promoting wound healing were prescribed by a veterinarian). A total of 31 treatment decisions (55 %) with creams containing anti-bacterial, anti-mycotic and/or anti-inflammatory agents and 100 % of systemic medications containing anti-bacterial, anti-parasitic or anti-inflammatory agents were prescribed by veterinarians. Overall, 69 % of treatment decisions were made without consulting a veterinarian, making it then more difficult to determine underlying causes for the pastern dermatitis and rendering the treatment often longer and more onerous. To raise owner awareness of possible consequences if a veterinarian is consulted too late in the disease process, specific information campaigns to improve animal welfare should be considered.

Background: In canine leishmaniosis (CanL) endemic areas, pathologists often receive skin biopsies for testing with histopathologic findings suggestive-but not conclusive for a definitive diagnosis-of CanL lesions. I the absence of data on the infective status of animals, the diagnosis can therefore be challenging. The aim of this retrospective study was to evaluate the ability of immunohistochemistry (IHC) and quantitative PCR (qPCR) methods to detect Leishmania infection in skin biopsies with a histopathologic diagnosis of lymphoplasmacytic/histiocytic and/or granulomatous dermatitis and to correlate the pattern, depth and severity of the histopathologic lesions with the parasite load detected by qPCR and IHC., Methods: Thirty formalin-fixed, paraffin-embedded skin samples were evaluated by hematoxylin-eosin (H&E) staining, IHC, conventional PCR (cPCR) and qPCR. The severity, pattern and depth of the dermal inflammation and parasite load were graded., Results: Leishmania was detected by H&E staining in 8/30 sections (26.66%) and by IHC in 14/30 samples (46.66%). Parasite DNA was detected in 14/30 samples (46.66%) by cPCR and in 21/30 samples (70%) by qPCR, with an extremely variable parasite load (1.32-62.700 copies). The level of agreement was fair between H&E staining and cPCR (κ = 0.32), and moderate between H&E staining and IHC (κ = 0.58). The level of agreement between IHC and cPCR was good (κ = 0.65); between IHC and qPCR, moderate (κ = 0.41); and between cPCR and qPCR, fair (κ = 0.28). A significant association was found between the severity of dermal inflammation and the parasitic skin load by IHC, although with weak linear correlation., Conclusions: Our study underlines the difficulty of obtaining a definitive diagnosis of CanL cutaneous lesions, even with the most accurate diagnostic tests currently available. Based on our results, no single test is suitable on its own for the diagnosis of cutaneous lesions caused by Leishmania. However, in the presence of a moderate/severe lymphoplasmacytic/histiocytic and/or granulomatous dermatitis, we suggest performing IHC, as in our study this technique proved to be the method with the highest discriminatory power to estimate the role of the parasite in skin lesions. In mild lesions, IHC loses its discriminatory power and should be effectively combined with techniques such as qPCR., (© 2022. The Author(s).)

Introduction: Due to venous insufficiency, a vascular ulcer frequently occurs with the progression of stasis dermatitis. Achromic melanoma, a rare form of pigmentless melanoma frequently located on the sole of the foot, is often and easily confused with a typical wound. Diagnosis of ulcerated achromic melanoma is thus often delayed and associated with a poor prognosis., Case Report: The authors report a very rare case of malignant melanoma in a 70-year-old female with stasis dermatitis. The painless ulcer was present for 1 year before the first visit. Upon clinical examination, a 2-cm diameter hypergranulating ulcer with irregular and pigmented borders was present. Dermoscopy revealed the presence of red globules, a gray-to-blue veil, irregular vessels, and the remains of a pigmented ridge pattern. Histological analysis showed infiltration of atypical melanocytes in the dermis, 2 mitoses, and ulceration. Diagnosis of melanoma was confirmed by positive MART-1 immunochemistry. After removal of the melanoma, the area was covered with an autologous skin graft excised from the inner thigh. In accordance with the guidelines, sentinel lymph node biopsy was performed, and the result was negative for lymph node involvement. A comprehensive clinical dermoscopic evaluation led to the correct diagnosis., Conclusions: The current case highlights the importance of evaluating a chronic, atypical, nonhealing ulcer clinically and dermoscopically as well as through a biopsy procedure.

Reactive granulomatous dermatitis (RGD) is a rare dermatosis with a variety of cutaneous manifestations unified by a dermal granulomatous infiltrate on histology. Rheumatoid arthritis and autoimmune disease are classic associations, but an increasing number of cases have been attributed to covert malignancy. Only 41 cases of paraneoplastic RGD have been documented to our knowledge and we present an additional case that manifested eight months prior to the diagnosis of ovarian cancer and clinically mimicked morphea. Histopathologic examination identifying palisaded CD68+ cells and collagen degeneration are helpful in diagnosing this entity which may mimic a host of other cutaneous processes, including metastatic disease. Cancer-directed therapies have been successful in clearing paraneoplastic RGD with or without the addition of corticosteroids, as RGD severity may be driven by the underlying malignancy. This case highlights the importance of utilizing histopathology to confirm the diagnosis given its nonspecific clinical findings, as well as the importance of considering malignancy and metastatic disease in patients diagnosed with RGD regardless of their cancer history.

Background: Rarely, Malassezia otitis presents as a painful, erosive otitis with an otic discharge containing Malassezia and neutrophils on cytology. There are no published reports of this type of suppurative Malassezia otitis (SMO). The role of Malassezia hypersensitivity in otitis is still unknown, and no association has been demonstrated with SMO. We compared Malassezia IgE levels, intradermal test and histology changes in SMO dogs with the more conventional Malassezia otitis (MO) presentation., Results: Three dogs (case 1, case 2 and case 3) were diagnosed with SMO, one dog (case 4) was diagnosed with unilateral MO and unilateral SMO, and one dog (case 5) was diagnosed with MO. Only one case (case 4) with SMO/MO had a positive Intradermal Allergy Test (IDAT) and elevated IgE levels for Malassezia. Histopathology findings from SMO revealed: interface dermatitis (case 1 and 3), lymphocytic dermatitis (case 2) and chronic hyperplastic eosinophilic and lymphoplasmacytic dermatitis (case 4). Histopathology findings from MO showed perivascular dermatitis (case 4 and 5). All the cases were treated successfully., Conclusions: SMO presents with a distinct clinical phenotype in comparison with conventional MO. No consistent aetiology could be isolated. In these clinical cases it is possible that previous treatments could have influenced the results. More research is needed to understand the possible aetiologies and the pathogenesis of SMO., (© 2021. The Author(s).)

Background: Caryospora bigenetica is an intracellular protozoan parasite, which in its primary hosts, typically snakes, is found it the intestine. Extraintestinal multiplication with the development of tissue cysts takes place in secondary hosts, which are normally prey for snakes. Natural infection in domestic animals has been reported only in dogs; this is the first report of C. bigenetica infection in a cat., Case Presentation: A stray kitten developed nodular dermatitis after being adopted by a shelter. Firm swelling, nodules, and crusts were present mainly on the nasal bridge, eyelids, and pinnae. Histopathology and cytology revealed severe pyogranulomatous inflammation with abundant intracellular organisms suggestive of apicomplexan protozoa. Treatment with clindamycin 13 mg/kg twice daily was initiated, but the cat was euthanized because of the worsening condition. Transmission electron microscopy confirmed parasite's apicomplexan origin postmortem, and the causative agent was identified as C. bigenetica by polymerase chain reaction and DNA sequencing., Conclusions: We present the first case of a naturally occurring infection with C. bigenetica in a cat. Although the definitive etiological diagnosis relied on molecular identification, the abundance of unsporulated oocysts and caryocysts and the parasite's effective reproduction within macrophages and in several other cell types might have enabled differentiation from other protozoal infections and allowed a presumptive diagnosis through cytology and histopathology., (© 2021. The Author(s).)

Patients on dialysis may have an elevated risk of severe coronavirus disease 2019 (COVID-19) and its complications due to their high prevalence of comorbidities. Here we describe the case of an 80-year-old male undergoing peritoneal dialysis with a moderate SARS-CoV-2 infection who developed a purpuric dermatitis and ischemic stroke after successful recovery from his bilateral pneumonia. Erythemato-papular lesions affecting trunk and lower limbs appeared 17 days after the onset of SARS-CoV-2 symptoms. These kind of lesions are an infrequent cutaneous manifestation of COVID-19. The pathology revealed a moderate purpuric dermatitis affecting superficial dermis and corticoesteroids were prescribed achieving complete resolution. Arterial thrombosis affecting cerebellar vermis emerged 30 days after the onset of COVID-19 symptoms. It occurred 5 days after withdrawal of antithrombotic prophylaxis that the patient received from his admission until 2 weeks after discharge. He completely recovered from his paresis and continued on his regular antiaggregation therapy. This is the first case report published of a patient with PD with such COVID-19-related complications. More experience is needed to determine the appropriate length of antithrombotic prophylaxis especially in high-risk individuals.

Circulating memory T cells are heterogeneous in their tissue tropism. The skin-seeking T cell subset expresses the cutaneous lymphocyte-associated antigen (CLA) on their surface. CLA + memory T cells not only migrate from blood to skin but also recirculate between blood and skin. Studying CLA + memory T cells in cutaneous diseases has allowed a better understanding of immune-inflammatory mechanisms that take place. The analysis of the phenotypical features of these cells, their antigen specificity, cytokine production profile, and changes in relationship to clinical status and therapies among other characteristics have led to the concept that they constitute peripheral cellular biomarkers in T cell-mediated cutaneous conditions. CLA + memory T cells are of relevance in the pathogenesis of several cutaneous diseases, such as psoriasis (PSO), atopic dermatitis, vitiligo, and drug-induced allergic reactions, to name a few. The interaction of circulating CLA + T cells with skin-resident cells has been investigated in different ex vivo coculture models made out of clinical samples. Interestingly, microbes that are present in the skin or related with human skin diseases are preferentially recognized by CLA + T cells. Thus, the interaction of Streptococcus pyogenes with CLA + T cells in PSO is providing novel concepts that help to understand disease immunopathogenesis. The goal of this review is to present latest results in the field of CLA + T cells in T cell-mediated inflammatory skin diseases and their translational relevance for human immunodermatology., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 de Jesús-Gil, Sans-de SanNicolàs, García-Jiménez, Ferran, Celada, Chiriac, Pujol and Santamaria-Babí.)

A 1-year-old, castrated, male, domestic short-haired cat with pruritic, multifocal, crusted ulceration of the skin over the dorsal aspect of the neck and scapulae was presented. The cat also had a history of depression and anorexia. A causative agent for the lesion was not identified on a general dermatological examination. Histopathology revealed diffuse epidermal ulceration and loss with replacement by neutrophilic inflammation and necrotic debris. Idiopathic ulcerative dermatitis (IUD) was diagnosed based on history, physical examination and histopathology. To prevent self-trauma and secondary bacterial infection, light bandages and glucocorticoid ointment were applied. After a month of management, the lesions markedly improved. Approximately 3 months after the initial presentation, the cat died; necropsy confirmed an IUD and non-effusive (dry form) feline infectious peritonitis (FIP). This report describes a rare case of IUD in a cat with concurrent FIP. However, no association between IUD and FIP was found., (© 2020 The Authors. Veterinary Medicine and Science Published by John Wiley & Sons Ltd.)

Heat shock proteins (Hsp) are constitutive and stress-induced molecules which have been reported to impact innate and adaptive immune responses. Here, we evaluated the role of Hsp70 as a treatment target in the imiquimod-induced, psoriasis-like skin inflammation mouse model and related in vitro assays. We found that immunization of mice with Hsp70 resulted in decreased clinical and histological disease severity associated with expansion of T cells in favor of regulatory subtypes (CD4 + FoxP3 + /CD4 + CD25 + cells). Similarly, anti-Hsp70 antibody treatment led to lowered disease activity associated with down-regulation of pro-inflammatory Th17 cells. A direct stimulating action of Hsp70 on regulatory T cells and its anti-proliferative effects on keratinocytes were confirmed in cell culture experiments. Our observations suggest that Hsp70 may be a promising therapeutic target in psoriasis and potentially other autoimmune dermatoses., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Tukaj, Mantej, Sobala, Potrykus, Tukaj, Zillikens, Ludwig, Bieber and Kasperkiewicz.)

Background: Palisaded neutrophilic granulomatous dermatitis is a rare cutaneous manifestation in children associated with autoimmune pathologies. The exact pathogenesis of this disease is still unknown. However, it has been suggested that the deposition of immune complexes could initiate this pathology., Case Report: We describe the case of an 11-year-old female patient who presented with polymorphic lesions in extremities associated with polyarthralgia. She was diagnosed with systemic lupus erythematosus and lupus nephritis. Because of the skin lesions, histopathological and immunohistochemical skin studies (CD68, CD163, myeloperoxidase) were performed, which resulted in palisaded neutrophilic granulomatous dermatitis. Due to renal involvement, treatment was administered with methylprednisolone pulses, hydroxychloroquine, mycophenolate mofetil, antihypertensives, and nonsteroidal anti-inflammatory drugs. The clinical response was favorable during follow-up., Conclusions: Palisaded neutrophilic granulomatous dermatitis associated with systemic lupus erythematosus is unusual. Therefore, its recognition is important, as it may appear as the initial manifestation of this autoimmune disease., (Copyright: © 2021 Permanyer.)

Hyper-immunoglobulin E syndrome (HIES) is a primary immunodeficiency disease characterized by recurrent Staphylococcus aureus ( S. aureus ) infections, eczema, skeletal abnormalities and high titers of serum immunoglobulin E. Although the genetic basis of HIES was not known for almost a half century, HIES most frequently exhibits autosomal dominant trait that is transmitted with variable expressivity. Careful genetic studies in recent years identified dominant-negative mutations in human signal transducer and activator of transcription 3 ( STAT3 ) gene as the cause of sporadic and dominant forms of HIES. The STAT3 mutations were localized to DNA-binding, SRC homology 2 (SH2) and transactivating domains and disrupted T helper 17 (T H 17) cell differentiation and downstream expression of T H 17 cytokines IL-17 and IL-22. Deficiency of IL-17 and IL-22 in turn is responsible for suboptimal expression of anti-staphylococcal host factors, such as neutrophil-recruiting chemokines and antimicrobial peptides, by human keratinocytes and bronchial epithelial cells. T H 17 cytokines deficiency thereby explains the recurrent staphylococcal lung and skin infections of HIES patients.

is missing (Short communication).

Background: Subtenon injection of triamcinolone acetonide (STTA) has been widely adopted in the clinical setting of ophthalmology and its infectious complications are rare. However, orbital abscess following STTA has been reported in seven cases. Furthermore, although eye infections due to Exophiala species are uncommon, there have been 19 cases to date. E. jeanselmei, E. phaeomuriformis, E. werneckii, and E. dermatitidis have been reported to cause human eye infections; however, to the best of our knowledge, orbital abscess caused by E. dermatitidis has not yet been reported. We describe the first documented case of fungal orbital abscess caused by E. dermatitidis following STTA. We also review the related literature of orbital abscess following STTA, as well as eye infections caused by the four Exophiala species., Case Presentation: The patient was a 69-year-old Japanese woman with diabetic mellitus. She had a macular oedema in her right eye, which occurred secondary to branch retinal vein occlusion. An orbital abscess caused by E. dermatitidis occurred 4 months after the second STTA for the macular oedema, which was successfully treated by a surgical debridement and systemic administration of voriconazole., Conclusions: Our findings in the patient and from our literature survey caution ophthalmologists to the fact that STTA can cause fungal orbital infections, especially in diabetic patients. Furthermore, surgical treatment is one of the most important risk factors.

BACKGROUND Obesity is one of the leading causes of preventable death worldwide. Due to its increasing incidence and the difficulty in reducing its morbidity and mortality using nonsurgical methods, the demand for bariatric surgery has risen in recent times. Sleeve gastrectomy is one of the most common types of bariatric surgery, and like any other surgery, it carries a series of risks. CASE REPORT Although complications such as gastrointestinal leaks are widely reported, there is limited literature available on cutaneous complications. Here, we report 4 cases of patients showing a peculiar skin rash 2-4 weeks following sleeve gastrectomy. We also discuss some of the mechanisms that may underlie this correlation. CONCLUSIONS There is a need for further epidemiological studies to determine the prevalence of this rash. Further studies are also needed to determine the exact etiology of this rash.

Interleukin (IL)-24 is a member of the IL-20 family of cytokines and is produced by various types of cells, such as CD4 + T cells, NK cells, mast cells, keratinocytes, bronchial epithelial cells, and myofibroblasts. Previous studies suggest that IL-24 plays an essential role in the pathogenesis of pro-inflammatory autoimmune disorders such as psoriasis, arthritis, and inflammatory bowel diseases. However, the role of IL-24 in the pathogenesis of allergic diseases has been elusive. It has already been reported that IL-24 is involved in the pathogenesis of allergic lung and skin diseases. Moreover, we have recently revealed for the first time the pivotal functions of IL-24 in IL-13-mediated skin barrier dysfunction in atopic dermatitis (AD), which is known to be a characteristic of AD caused by Th2 cytokines such as IL-4 or IL-13. In this review, we show recent advances in the basic characteristics of IL-24 and its novel functions in the pathogenesis of allergic skin inflammation, focusing on AD. A better understanding of the role of IL-24 in allergic diseases can lead to the development of new therapeutic options., (Copyright © 2019 Japanese Society of Allergology. Production and hosting by Elsevier B.V. All rights reserved.)