Atopy and Elevation of IgE, IgG3, and IgG4 May Be Risk Factors for Post COVID-19 Condition in Children and Adolescents.

SARS-CoV-2 infection causes transient cardiorespiratory and neurological disorders, and severe acute illness is rare among children. Post COVID-19 condition (PCC) may cause profound, persistent phenotypes with increasing prevalence. Its manifestation and risk factors remain elusive. In this monocentric study, we hypothesized that atopy, the tendency to produce an exaggerated immunoglobulin E (IgE) immune response, is a risk factor for the manifestation of pediatric PCC. We present a patient cohort (n = 28) from an early pandemic period (2021-2022) with comprehensive evaluations of phenotypes, pulmonary function, and molecular investigations. PCC predominantly affected adolescents and presented with fatigue, dyspnea, and post-exertional malaise. Sensitizations to aeroallergens were found in 93% of cases. We observed elevated IgE levels (mean 174.2 kU/L, reference < 100 kU/L) regardless of disease severity. Concurrent Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) was found in 29% of patients that also faced challenges in school attendance. ME/CFS manifestation was significantly associated with elevated immunoglobulin G subclasses IgG3 (