BACKGROUND: Individuals with inflammatory bowel disease (IBD) exhibit a heightened likelihood of developing erythema nodosum (EN), but the presence of causal link is unknown. The purpose of the present research was to investigate this connection using a bidirectional two-sample Mendelian randomization (MR) analysis.
METHODS: Summarized statistics for EN were sourced from the FinnGen consortium of European ancestry. The International Inflammatory Bowel Disease Genetic Consortium (IBDGC) was used to extract summary data for IBD. The inverse variance weighted (IVW) technique was the major method used to determine the causative link between them.
RESULTS: The study evaluated the reciprocal causal link between IBD and EN. The IVW technique confirmed a positive causal link between IBD and EN (OR = 1.237, 95% CI: 1.109-1.37, p = 1.43 × 10- 8), as well as a strong causality connection between Crohn\'s disease (CD) and EN (OR = 1.248, 95% CI: 1.156-1.348, p = 1.00 × 10- 4). Nevertheless, a causal connection between ulcerative colitis (UC) and EN could not be established by the data. The reverse MR research findings indicated that analysis indicated that an increase in EN risks decreased the likelihood of UC (OR = 0.927, 95% CI: 0.861-0.997, p = 0.041), but the causal association of EN to IBD and CD could not be established.
CONCLUSIONS: This investigation confirmed that IBD and CD had a causal connection with EN, whereas UC did not. In addition, EN may decrease the likelihood of UC. Further study must be performed to uncover the underlying pathophysiological mechanisms producing that connection.

Idiopathic granulomatous mastitis (IGM) is a noncancerous, chronic inflammatory disorder of breast with unknown causes, posing significant challenges to the quality of life due to its high refractoriness and local aggressiveness. The typical symptoms of this disease involve skin redness, a firm and tender breast mass and mastalgia; others may include swelling, fistula, abscess (often without fever), nipple retraction, and peau d\'orange appearance. IGM often mimics breast abscesses or malignancies, particularly inflammatory breast cancer, and is characterized by absent standardized treatment options, inconsistent patient response and unknown mechanism. Definite diagnosis of this disease relies on core needle biopsy and histopathological examination. The prevailing etiological theory suggests that IGM is an autoimmune disease, as some patients respond well to steroid treatment. Additionally, the presence of concurrent erythema nodosum or other autoimmune conditions supports the autoimmune nature of the disease. Based on current knowledge, this review aims to elucidate the autoimmune-favored features of IGM and explore its potential etiologies. Furthermore, we discuss the immune-mediated pathogenesis of IGM using existing research and propose immunotherapeutic strategies for managing this condition.

BACKGROUND: Previous studies have demonstrated the coexistence of erythema nodosum (EN) and inflammatory bowel disease (IBD), while the exact etiology of the co-occurrence of the two disorders remains uncertain.
METHODS: A bidirectional two-sample Mendelian randomization (MR) design was employed to determine the causal link between EN and IBD. Genetic variations associated with Crohn\'s disease (CD) and ulcerative colitis (UC) were derived from accessible genome-wide association studies pertaining to European ancestry. The FinnGen database was used to find the genetic variations containing EN. In the forward model, IBD was identified as the exposure, whereas in the reverse model, EN was identified as the exposure. The causal link between IBD and EN was examined using a range of different analysis techniques, the primary one being the inverse variance weighted (IVW) method, including inverse variance weighted-fixed effects (IVW-FE) and inverse-variance weighted-multiplicative random effects (IVW-MRE). To strengthen the results, assessments of sensitivity, heterogeneity, and pleiotropy were also conducted.
RESULTS: MR results showed that IBD increased the risk of EN (IVW-MRE: OR = 1.242, 95% CI = 1.068-1.443, p = 0.005). Furthermore, there was a strong correlation found between CD and a higher risk of EN (IVW-FE: OR = 1.250, 95% CI = 1.119-1.396, p = 8.036 × 10-5 ). However, UC did not appear to be linked to EN (IVW-FE: OR = 1.104, 95% CI = 0.868-1.405, p = 0.421). The reverse MR analysis findings did not imply that EN was linked to IBD. Horizontal pleiotropy did not appear to exist, and the robustness of these findings was confirmed.
CONCLUSIONS: The current investigation found that in European populations, IBD and its subtype CD could raise the incidence of EN.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease typically involving the gastrointestinal tract but not limited to it. IBD can be subdivided into Crohn\'s disease (CD) and ulcerative colitis (UC). Extraintestinal manifestations (EIMs) are observed in up to 47% of patients with IBD, with the most frequent reports of cutaneous manifestations. Among these, pyoderma gangrenosum (PG) and erythema nodosum (EN) are the two most common skin manifestations in IBD, and both are immune-related inflammatory skin diseases. The presence of cutaneous EIMs may either be concordant with intestinal disease activity or have an independent course. Despite some progress in research on EIMs, for instance, ectopic expression of gut-specific mucosal address cell adhesion molecule-1 (MAdCAM-1) and chemokine CCL25 on the vascular endothelium of the portal tract have been demonstrated in IBD-related primary sclerosing cholangitis (PSC), little is understood about the potential pathophysiological associations between IBD and cutaneous EIMs. Whether cutaneous EIMs are inflammatory events with a commonly shared genetic background or environmental risk factors with IBD but independent of IBD or are the result of an extraintestinal extension of intestinal inflammation, remains unclear. The review aims to provide an overview of the two most representative cutaneous manifestations of IBD, describe IBD\'s epidemiology, clinical characteristics, and histology, and discuss the immunopathophysiology and existing treatment strategies with biologic agents, with a focus on the potential pathophysiological associations between IBD and cutaneous EIMs.

UNASSIGNED: Granulomatous lobular mastitis (GLM) is a benign inflammatory disease of the mammary gland with unknown etiology. Erythema nodosum (EN) is a rare, extramammary symptom of GLM. The purpose of this article was to investigate the clinical features of EN associated with GLM.
UNASSIGNED: We recruited 102 GLM patients diagnosed between December 2018 and December 2021 at Renmin Hospital of Wuhan University. The clinical characteristics and laboratory indices of the EN group (n = 12) and the non-EN group (n = 90) were compared.
UNASSIGNED: The proportion of GLM patients with lesions involving ≥2 quadrants and high peripheral white blood cell count, absolute neutrophil count and neutrophil-to-lymphocyte ratio (NLR) was larger in the EN group than in the non-EN group (p = 0.002, 0.025, 0.014, 0.002, respectively). The duration of EN was longer in GLM patients with EN than in GLM patients without EN (p = 0.005). GLM patients with EN had more abscesses and sinus tracts than those without EN (p = 0.003, 0.038). Lesions involving ≥2 quadrants and the NLR were positively associated with the occurrence of EN (R = 0.304, 0.0302, p = 0.002, 0.002). Receiver operating characteristic curve analysis revealed that the area under the curve of the NLR was 0.770. When NLR > 5.73, the sensitivity and specificity of predicting EN were 66.67% and 87.78%, respectively.
UNASSIGNED: Our findings suggest that GLM concomitant with EN suggests the presence of a more severe condition and extensive lesions.

Goserelin acetate is a gonadotropin-releasing hormone analog that is commonly used in patients with prostate cancer, endometriosis, and precocious puberty. The side effects of the drug include allergic rash, flushing, excessive sweating, skin swelling at the injection site, sexual dysfunction, erectile dysfunction, and menopausal symptoms. However, erythema nodosum has so far not been reported. In this paper, we have presented the case of erythema nodosum caused by goserelin acetate and a review of the literature on its adverse effects, thus providing useful insights into clinical management and medication safety.

This experiment was carried out to investigate changes in lymphocyte subpopulation, immunoglobulins (Igs), and complements, and also to explore the relationship between these immune indices and C-reactive protein and erythrocyte sedimentation rate in 61 patients with erythema nodosum. For this aim, a 4-year, retrospective study contained 61 patients with erythema nodosum, and 61 healthy control subjects were included from the out-patient clinic. The subpopulation of the T, B and natural killer lymphocytes and levels of IgA, IgG, IgM, complement C3, complement C4, C-reactive protein, and erythrocyte sedimentation rate from peripheral blood of them were detected. A correlation analysis was done between lymphocyte subpopulation, levels of IgA, IgG, and IgM, complement C3, complement C4 and C-reactive protein level and erythrocyte sedimentation rate in the patient group. Results showed that the percentage of CD4+ cells, CD4+/CD8+ ratio, the level of C-reactive protein and the erythrocyte sedimentation rate in the patients were higher than in controls (P<0.05). While the percentage of CD8+ cells and the serum levels of complement C3 were lower than in controls (P<0.05). There were no differences in the percentages of CD3+, B and natural killer cells and the serum levels of IgA, IgG and IgM, and complement C4 between the patients and the controls (P>0.05). IgM level was positively correlated with C-reactive protein (P<0.05) but did not correlate with an erythrocyte sedimentation rate (P>0.05). There was no correlation between lymphocyte subpopulation, levels of IgA, IgG, complement C3, complement C4 and C-reactive protein level and erythrocyte sedimentation rate (P>0.05). In conclusion, there was dysregulation of both cellular immunity and humoral immunity in patients with erythema nodosum. IgM level has a positive correlation with C-reactive protein.

Cutaneous nocardiosis is a rare bacterial infection that can result in various dermatologic manifestations such as actinomycetoma, lymphocutaneous infection, superficial skin infection, and secondary infection due to hematogenous dissemination. We report on a Chinese patient with erythema nodosum-like exanthema, possibly secondary to nocardiosis. Our diagnosis for this patient was based on the clinical presentation, histopathological evidence, and microbiological findings. Given the protean manifestation of Nocardia, persistent reports on new presentations of the disease are important for early identification and treatment.

BACKGROUND: Behçet\'s disease (BD) is an autoimmune disease presented with recurrent oral aphthous ulcers, genital ulcers, uveitis and skin lesions. The cutaneous manifestations are often refractory and more resistant to conventional therapy. This report provides a new treatment of low-dose interleukin-2 (IL-2) with refractory BD patient.
METHODS: A 37-year-old female patient experienced oral ulcer and erythema nodosum on the right leg for over 12 months and resisted to Methylprednisolone and Thalidomide.
METHODS: The patient suffered from recurrent painful oral ulceration and an erythema nodosum. Pathergy test is also positive. Thus, we diagnosed her as BD according to the International Criteria for Behçet\'s Disease (ICBD).
METHODS: The patient took Methylprednisolone 8 mg qd, Thalidomide 50 mg qn and Hydroxychloroquine 200 mg bid successively as treatment. However, the medicine didn\'t take effect. Finally, this patient was given low-dose IL-2 intramuscular injection qod for 3 months.
RESULTS: Oral ulcers and the erythema disappeared and the patient has been symptom-free for 6 months.
CONCLUSIONS: low-dose IL-2 is a safe and effective treatment for refractory BD.

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