Aim: To assess abnormalities in red blood cell parameters, iron metabolism, and vitamin B12 status in children with obesity, and to evaluate the influence of dietary intake and obesity-related complications on these variables. Methods: A retrospective analysis was conducted in 152 children with obesity. Anthropometric, biochemical, and hematological parameters were assessed. Dietary intake was evaluated in a subgroup of 33 participants using 3-day food records. Results: No cases of low hemoglobin levels were identified. However, elevated TIBC and occasional low ferritin levels suggested disturbances in iron metabolism. BMI Z-score was positively associated with red blood cell count and selected iron metabolism markers, whereas higher body fat percentage was negatively associated with hemoglobin and hematocrit. Dietary analysis indicated that protein and vitamin B12 intake were associated with erythrocyte parameters, while no associations were found for iron or folate intake. Elevated liver enzymes were associated with higher hemoglobin, hematocrit, and MCV values. Conclusions: Pediatric obesity was not associated with low hemoglobin levels but may be linked to early, subclinical disturbances in iron metabolism. These findings should be confirmed using more comprehensive biomarkers. Dietary factors, particularly vitamin B12 intake, may contribute to variability in erythrocyte parameters; however, these associations should be interpreted with caution. The observed relationship between liver function and erythrocyte indices warrants further investigation.

Hemolytic-uremic syndrome (HUS) is a thrombotic microangiopathy that is most commonly caused by infection with Shiga toxin-producing Escherichia coli (STEC-HUS). Atypical HUS (aHUS) is associated with inappropriate activation of the alternative complement pathway caused by infections, including SARS-CoV-2, malignancies, medications, or other triggering factors in genetically predisposed individuals. Assessment of the impact of the COVID-19 pandemic on epidemiology, course, complications, and outcome of HUS in children in a single tertiary nephrological center in Poland. It is a retrospective study, in which a total number of 74 pediatric patients with HUS were analyzed, including 16 cases in 5-year period before the outbreak of the COVID-19 pandemic (HUS-5) and 58 cases in 5-year period after the outbreak of the pandemic (HUS+5). A more than 3.6-fold increase in HUS cases and a 7-fold higher incidence of STEC-HUS were reported in the HUS+5 population. Strokes and persistent neurological complications were observed only in this group. 91.9% of patients presented with abnormal renal ultrasound (USG) findings at admission, and these findings improved significantly more frequently in the HUS-5 (68.75% vs 25.9%, p = 0.002) group. Mortality did not differ significantly between the 2 analyzed groups and was 6.8% for the entire population. The COVID-19 pandemic has had a significant impact on the incidence of HUS in the pediatric population. SARS-CoV-2 infection most markedly increases the risk of neurological complications but does not affect overall mortality.