Type 4 renal tubular acidosis (RTA) is an uncommon but clinically significant complication in kidney transplant recipients, leading to hyperkalemia and non-anion gap metabolic acidosis due to aldosterone deficiency or resistance. Calcineurin inhibitors, especially tacrolimus, can contribute to this disorder by impairing distal tubular potassium secretion. We describe a 47-year-old male who underwent living donor kidney transplantation from his biological mother. Despite good early graft function, he developed severe recurrent hyperkalemia, requiring hemodialysis on postoperative days 11 and 23. Laboratory evaluation revealed non-anion gap metabolic acidosis (anion gap 10.8 mEq/L), urine pH 5.5, and a low transtubular potassium gradient of 2.5, consistent with type 4 RTA. At diagnosis, serum creatinine was 1.39 mg/dL (estimated glomerular filtration rate, 54.8 mL/min/1.73 m 2 ). The patient was treated with fludrocortisone (starting at 0.2 mg/day and tapered to 0.05 mg/day), a thiazide diuretic (12.5 mg twice daily), and reduction of tacrolimus dose with addition of sirolimus (2.5 mg/day). Electrolyte abnormalities resolved, and graft function remained stable without rejection. This case underscores the importance of recognizing tacrolimus-induced type 4 RTA early and using individualized treatment strategies to correct hyperkalemia and preserve allograft function.

Purpose: Based on the KEYNOTE-522 study, neoadjuvant pembrolizumab plus chemotherapy has become the standard treatment for early-stage triple-negative breast cancer (TNBC).This study evaluated the real-world efficacy, safety, and predictors of pathologic complete response (pCR) in Korean patients. Methods: We conducted a retrospective cohort study of 174 patients with early-stage TNBC who received the KEYNOTE-522 regimen (neoadjuvant pembrolizumab plus paclitaxel and carboplatin, followed by doxorubicin and cyclophosphamide) at a tertiary cancer center between August 2022 and July 2024. We assessed the primary endpoints, including pCR rate and event-free survival (EFS). We performed univariable and multivariable logistic regression analyses to identify independent predictors of pCR. Results: The median patient age was 50 years (range, 24–74 years). The clinical stages were II and III in 79.3% and 20.1% of patients, respectively, and 10.9% had clinical N3 disease. The overall pCR rate was 62.1%, and the N3 subgroup had a pCR rate of 47.4%. On multivariable analysis, high baseline Ki-67 expression (≥ median, 75%) was significantly associated with pCR (odds ratio, 2.84; 95% confidence interval, 1.45 to 5.66; p = 0.002). At a median followup of 18.4 months, the 12-month EFS rate was 97.4%, with significantly superior outcomes observed in patients who achieved pCR compared with those who did not achieve pCR (100% vs. 93.1%, p = 0.007). The treatment completion rate was 92.0%, and immune-related adverse events occurred in 13.8% of patients. Conclusion In this real-world analysis of one of the largest Asian cohorts of patients with earlystage TNBC treated with neoadjuvant pembrolizumab, the KEYNOTE-522 regimen demonstrated substantial efficacy and manageable toxicity, consistent with the original trial findings.

Ischemic neuropathy is an uncommon cause of peripheral nerve injury that results from compromised blood flow or oxygen delivery to the vasa nervorum. We report a rare case of multiple ischemic mononeuropathies of the right lower limb that developed after percutaneous coronary intervention (PCI). A 57-year-old man who underwent PCI for ST-elevation myocardial infarction presented with persistent weakness, sensory disturbance, and pain in the right lower limb. Electrodiagnostic studies performed 4 weeks after symptom onset revealed findings consistent with multiple mononeuropathies of the right lower limb. In cases of ischemic neuropathy associated with arterial occlusion, prompt vascular imaging and revascularization of the occluded artery are essential to minimize neurological deficits and optimize motor recovery.

Background/Aims: We examined the association between diabetes duration and hyperuricemia in Korean subjects based on data from the Korea National Health and Nutrition Examination Survey (KNHANES). Methods: This cross-sectional study included 4,575 subjects aged 30 years and older with type 2 diabetes mellitus based on data from the KNHANES from 2016 to 2021. Hyperuricemia was defined as a serum uric acid level ≥ 7.0 mg/dL. Univariable and multivariable logistic regression models were used calculate adjusted odds ratios (ORs) and their 95% confidence intervals (CIs). Results: The mean age of subjects was 61.0 years, 56.5% were male, and the mean body mass index (BMI) was 25.6 kg/m2. Compared to those with diabetes duration 5 to < 10 years, those with shorter or longer diabetes duration had higher serum uric acid levels and higher prevalence of hyperuricemia. In multivariable logistic regression models, a U-shaped association between diabetes duration and hyperuricemia was observed after adjusting for age, sex, income, smoking status, alcohol consumption, regular exercise, and presence of hypertension, dyslipidemia, or chronic kidney disease. Compared to those with new-onset diabetes mellitus, the adjusted OR (95% CI) for hyperuricemia was 0.55 (0.38–0.82) in those with diabetes duration 5 to < 10 years. The results were consistent in subgroup analysis according to age, sex, BMI, and chronic kidney disease. Conclusions The U-shaped association between diabetes duration and hyperuricemia was observed in a representative sample of Korean adults.

Rectal cancer, which accounts for approximately 40% of colorectal cancers, remains a major clinical concern. Recent advances in diagnostic imaging, surgical techniques, radiotherapy, and systemic treatment have steadily improved rectal cancer outcomes. Considering this, the Korean Rectal Cancer Multidisciplinary (KRCM) Committee has aimed to provide clinicians and policymakers with up-to-date, evidence-based clinical practice guidelines to support optimal decision-making, reflecting current evidence, the Korean healthcare context, and patient values and preferences. The Clinical Practice Guidelines for Rectal Cancer version 2.0 were developed through multidisciplinary collaboration with related academic societies, building upon and updating the KRCM Clinical Practice Guidelines version 1.0 (titled “Multidisciplinary guidelines for the management of rectal cancer”). These consensus guidelines of the KRCM were established based on a comprehensive literature review, evidence synthesis, with recommendation development guided by the GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology, and consideration of applicability in real-world clinical practice under the national health insurance system. Each recommendation has been presented with its strength and level of evidence.

Background: Rosacea is a chronic inflammatory skin disorder characterized by erythema, papules, ocular symptoms, and heightened sensitivity. Patients with neurogenic symptoms such as burning or stinging remain particularly difficult to manage. Current guidelines often underrepresent energy-based devices (EBDs), pigmentary sequelae, psychosocial burden, and ocular comorbidities. Objective: To examine Korean dermatologists’ expert perspectives on rosacea management, focusing on skin sensitivity, neurogenic symptoms, pigmentary changes, psychosocial impact, ocular involvement, and EBD use. Methods: A web-based, 29-item survey was administered to 25 board-certified Korean dermatologists (May–June 2025). Quantitative and qualitative responses were analyzed. Results: Erythematotelangiectatic and papulopustular phenotypes with sensitivity skin predominated. EBDs (pulsed dye laser, intense pulsed light) were frequently used but limited by cost and sensitivity issues. Neurogenic symptoms were recognized but rarely treated with neuromodulators. Post-inflammatory hyperpigmentation was infrequent, yet monitoring was inconsistent.Psychosocial and ocular aspects were acknowledged but seldomly systematically addressed.Respondents expressed interest in emerging adjunctive treatments such as cold plasma, skin boosters, and holistic care approaches. Conclusion Korean dermatologists adopt individualized strategies for rosacea, yet practice gaps remain regarding neurogenic symptoms, pigmentary complications, and psychosocial and ocular comorbidities. Findings support the need for updated multidisciplinary, phenotype-driven guidelines aligned with real-world practice.

Background: Erythema multiforme (EM) is typically a self-limited, acute hypersensitivity reaction. However, a subset of patients experiences chronic, recurrent episodes, for which clinical features and treatment strategies differ depending on the underlying etiology, especially in herpes simplex virus (HSV)-associated cases. Objective: To investigate the clinical and phenotypic features of chronic recurrent EM and assess treatment responses, with a focus on differences based on HSV association. Methods: This retrospective study included pathology-confirmed cases of suspected EM from 2010 to 2023. Forty patients with chronic EM (≥3 recurrences or persistent disease for ≥12 months) were included. Clinical, histopathologic, and serologic data were analysed.Patients were stratified into herpes simplex virus-associated erythema multiforme (HAEM) and non-HAEM groups. Clustering analysis was performed to identify clinical phenotypes.Treatment responses to antivirals and immunomodulators were evaluated. Results: Of the 40 patients, 24 (60%) were classified as HAEM. HAEM patients showed more mucosal involvement, smaller targetoid lesions, and acral predominance, while nonHAEM patients had larger, coalescing lesions with more trunk involvement. Cluster analysis supported HSV as the major discriminating factor. Antiviral agents were effective in 87.5% of HAEM cases but ineffective in 76.9% of non-HAEM patients. Immunosuppressants such as cyclosporine and mycophenolate mofetil showed variable responses. Baricitinib induced complete remission in all 3 refractory cases. Conclusion HSV association defines a distinct clinical subtype of chronic recurrent EM, with differences in lesion morphology, distribution, and treatment response. Recognizing these patterns may guide targeted therapeutic strategies, including the potential use of Janus kinase inhibitors in refractory cases.

The recent recognition of human epidermal growth factor receptor 2 (HER2)–low and HER2-ultralow breast cancers (BCs) has expanded the therapeutic relevance of HER2 testing in the antibody-drug conjugate era. However, the biological continuum of HER2 expression measured by immunohistochemistry (IHC) and its relationship with the HER2 gene copy number remain unclear. Methods: We retrospectively analyzed 135 HER2-negative invasive BCs and reclassified them as HER2-null (IHC 0), HER2-ultralow (0+), or HER2-low (1+ or 2+ without amplification). HER2 gene copy number was determined using silver-enhanced in situ hybridization. Statistical analyses were performed to compare HER2 copy number among IHC categories and evaluate the discriminatory value of HER2 copy number for distinguishing IHC subgroups. Results: The mean HER2 copy number increased stepwise across IHC categories: 1.95 ± 0.54 (null), 2.03 ± 0.43 (ultralow), 2.25 ± 0.65 (low, 1+), and 3.29 ± 1.05 (low, 2+). Significant differences were observed between the ultralow and low groups (p = .003) and between the null and low groups (p < .001), but not between the null and ultralow groups or between the ultralow and 1+ groups. Conclusions: HER2 gene copy number was positively correlated with protein expression as reflected by IHC categories. Although HER2 gene copy number was statistically higher in HER2-low than in HER2-null tumors, the substantial overlap in copy number ranges likely limits its utility in distinguishing HER2-low from HER2- null BCs.

This study aimed to determine the prevalence of human epidermal growth factor receptor 2 (HER2)–ultralow breast cancer among cases initially classified as HER2 immunohistochemistry (IHC) 0 and assess interobserver variability in interpreting low-level HER2 expression. Methods: In this multicenter retrospective study, all invasive breast cancer cases diagnosed between January and December 2022 across 10 Korean institutions were retrieved. Institutional pathologists reexamined HER2 IHC slides originally reported as IHC 0 according to the 2018 American Society of Clinical Oncology/College of American Pathologists guidelines and reclassified them as HER2-null (0), HER2-ultralow (0+), or HER2-low (1+). Slides from 10% of HER2-null and HER2-ultralow cases were digitized for central review and independently assessed by two pathologists, with discrepancies resolved by consensus. Results: Among 8,026 cases, 2,836 cases (35.5%) were initially reported as IHC 0. Upon re-review, 1,673 (59.0%), 1,139 (40.2%), and 24 (0.8%) cases were reclassified as HER2-null, HER2-ultralow, and HER2-low, respectively. The prevalence of HER2-ultralow breast cancer varied considerably across institutions (23.7%–78.1%). Central review of 268 digitized cases showed concordance in 193 cases (72.0%). Among the 75 discordant cases, 54 tumors (72.0%) were upgraded from HER2-null to HER2-ultralow, and 18 (24.0%) tumors were upgraded from HER2-ultralow to HER2-low. Furthermore, two tumors (2.7%) were downgraded from HER2-ultralow to HER2-null. Conclusions: Approximately 40% of cases initially categorized as IHC 0 were reclassified as HER2-ultralow. The substantial inter-institutional variability observed in interpreting low-level HER2 expression highlights the need for standardized training and quality assurance to ensure accurate identification of patients eligible for HER2-targeted antibody–drug conjugates.