Background: To address the public’s fear of coronavirus disease 2019 (COVID-19), understanding the clinical features of the disease is essential. However, research on the clinical features of COVID-19, including illness duration and post-acute COVID-19, in Korean pediatric patients has been limited. Therefore, this study investigated the clinical features of COVID-19 based on the medical records of pediatric patients with a history of COVID-19 who visited a single center. Methods: In total, 311 patients were included in this study. The presence and duration of 19 symptoms were examined. Additionally, clinical features were investigated by dividing the patients into different age ranges. Patients aged 6 and above were further categorized according to the presence of asthma, while adolescent patients were divided into vaccinated and unvaccinated groups.Results: Fever and cough were the most common symptoms. The mean illness duration was 2–4 days. Only 3.5% of the patients were asymptomatic. Post-acute COVID-19 was observed in 13.2% of the patients. The incidence of most symptoms tended to increase with age. Post-acute COVID-19 was observed more frequently in patients with asthma than in those without asthma. Vaccinated patients experienced less fever, vomiting, and fatigue than unvaccinated patients.Conclusions: Our data suggest that most patients had mild disease lasting less than a week, and the clinical course may differ depending on the presence of asthma. The findings also indicate that vaccination may alleviate the symptoms of COVID-19 in breakthrough infections.

You Min Kim, Young Hyun Kim, and Jin Kyung Kim. J Genet Med 2025;22:29-35. https://doi.org/10.5734/JGM.2025.22.1.29

Hydrops fetalis is a condition characterized by excessive fluid accumulation in the fetus, and is classified into immune and non-immune types depending on the underlying disease. Among cases of non-immune hydrops fetalis (NIHF), 15% to 20% are of cardiac origin, and genetic factors such as titin (TTN) gene mutations can contribute to cardiac dysfunction. We report the case of a preterm infant (29+2 weeks, 1,430 g) with hydrops fetalis who developed cardiac tamponade due to major pericardial effusion. Seven hours after birth, the heart rate suddenly decreased, and blood pressure could not be measured. Transthoracic echocardiography revealed substantial pericardial effusion and severely impaired cardiac function, and the preterm infant was diagnosed with pericardial tamponade. Emergency pericardiocentesis was performed, which led to hemodynamic stabilization. Genetic testing identified two heterozygous TTN mutations (c.13898A>T and c.27856G>T), with the latter presumed responsible for the observed cardiac dysfunction. The mother was found to carry the c.13898A>T mutation, but was asymptomatic. This case report highlights the importance of genetic testing in neonates with unexplained NIHF and cardiac complications. Identifying TTN gene mutations provides valuable insights into the underlying pathophysiology and guides clinical management.

Background/Objectives: Bronchopulmonary dysplasia (BPD) risk evolves as clinical information accumulates after birth. This study evaluated the incremental predictive value of routinely available data from birth through the first week of life using cumulative, time-aligned feature sets. Methods: The primary analysis of this retrospective cohort study included 2153 preterm infants who survived to 36 weeks’ postmenstrual age and had ascertainable BPD status and complete predictor data. The outcome was clinically documented BPD at 36 weeks’ postmenstrual age, based on the treating neonatologists’ assessment of continued supplemental oxygen and/or respiratory-support requirements. Three cumulative feature sets were constructed using variables available at or immediately after birth (Step 1), additional clinical and laboratory variables available within the first 24 h (Step 2), and further clinical-course variables available through postnatal day 7 (Step 3). Logistic regression, random forest, XGBoost, LightGBM, and CatBoost models were developed using a stratified 70:30 training–test split and five-fold stratified cross-validation. Internal validation assessed discrimination, calibration, and Brier scores in the held-out test set. AUROC confidence intervals and paired differences between prediction windows were estimated using 2000 bootstrap resamples. Predictor contributions were examined using SHapley Additive exPlanations. A multiple-imputation sensitivity analysis evaluated logistic regression and random forest in all 2616 infants with ascertainable BPD status. Results: Of the 2153 infants, 1154 (53.6%) had clinically documented BPD. Logistic regression achieved the highest held-out test-set AUROC at each prediction window: 0.751 (95% CI, 0.714–0.788) in Step 1, 0.897 (0.873–0.919) in Step 2, and 0.923 (0.902–0.942) in Step 3. Paired AUROC increases were 0.146 (95% CI, 0.110–0.181) from Step 1 to Step 2 and 0.026 (0.015–0.036) from Step 2 to Step 3. Logistic regression Brier scores decreased from 0.202 to 0.130 and 0.112, respectively. In the Step 3 logistic regression model, the leading predictors by mean absolute SHAP value were mean SpO₂ during the first 24 h, mean arterial pressure, initial feeding approach, FiO₂ at 24 h, and C-reactive protein. In the expanded sensitivity-analysis test cohort, logistic-regression AUROCs were 0.747, 0.893, and 0.913 for Steps 1–3, respectively. Conclusions: The addition of first-24 h clinical information substantially improved BPD prediction beyond birth variables, with further improvement from data accumulated through postnatal day 7. The primary analysis did not demonstrate an added predictive benefit of the evaluated tree-based algorithms over logistic regression. The primary findings apply to a selected cohort of survivors with complete data and should not be generalized to all initially eligible infants or interpreted as prediction of BPD or death. Temporal and external validation and prospective evaluation of clinical utility are required before implementation.