Asthma is one of the most common chronic diseases. Epidemiological studies show that asthma will develop among around 40% of children under six years old with symptoms of bronchial obstruction.Diagnosis of asthma is complicated, especially in the paediatric population. As a result, a lot of research is being carried out to establish the pathophysiology and to find new biomarkers of this disease. Progranulin (PGRN) is a recently discovered growth factor with many biological functions. PGRN has anti-inflammatory properties because it inhibits neutrophil degranulation and blocks tumor necrosis factor α (TNF-α) transmission. The underlying mechanisms are still being researched, but TNF-α is considered to be a cytokine responsible for neutrophilic inflammation in the airways and bronchial hyperresponsiveness. Therefore, PGRN, by lowering TNF-α concentration and stimulating regulatory T-cell (Treg) prolifera­tion, relieves symptoms of bronchial inflammatory diseases. This article attempts to verify the current knowledge about basic pathophysiological mechanisms in asthma. We also summarise the most recent research advances in the role of PGRN in the respiratory system.

Seasonal outbreaks of respiratory syncytial virus are common among young children and represent an important clinical problem. The infection can affect all floors of the respiratory system. Respiratory syncytial virus is highly infectious and is the most common aetiological agent of bronchiolitis. It is estimated that 90% of children develop respiratory syncytial virus infection by the age of 2 years. In Poland and other countries of the northern hemisphere, these infections usually occur between October and May, with a peak in January–February. During the global COVID-19 pandemic, a significant change was observed in the epidemiology of respiratory syncytial virus infections in Europe and worldwide. The massive use of nonpharmacological interventions, such as closing nurseries, kindergartens, limited interpersonal contact, social distancing, strict hygiene rules and the use of protective masks, resulted in the absence or episodic occurrence of many seasonal infections, including those of respiratory syncytial virus aetiology, in 2020. In 2021, a so-called compensatory epidemic of syncytial virus aetiology was observed, i.e. a significant increase in the incidence associated with the extinction of collective immunity and an increasing proportion of susceptible individuals. The aim of the present study was to retrospectively analyse the incidence of respiratory syncytial virus infections in children hospitalised in the Department of Paediatrics, Paediatric Nephrology and Allergology of the Military Institute of Medicine in Warsaw in the years 2020–2021. We also discussed the prevention and treatment of infections, as well as the association of bronchiolitis with the development of asthma in children.

Respiratory syncytial virus (RSV) is the most common pathogen causing bronchiolitis and pneumonia in children up to 24 months old. The virus infects 90% of children within the first 2 years of life, with the highest infection rates in children aged between 6 weeks and 6 months. The majority of cases occur in winter (January and February). Although RSV infection is usually mild, only 1% of children are asymptomatic. All levels of the respiratory system may be affected. Usually mild upper respiratory infections not requiring hospitalisation are observed. About 10% of infected children develop bronchiolitis. RSV infection is the cause of 17-20% of all infantile hospitalisations. Long-term studies have demonstrated a relationship between RSV and obstructive ventilatory disorders in the first decade of life. However, no clear cause and effect relationship was found in this case. It is supposed that RSV infection may only reveal the genetic predisposition to this type of response in children. The aim of the study was to analyse the course of RSV infection in a group of 71 children up to 24 months old. Attention was paid to risk factors, patient's age, gender distribution in the study group, the number of cases in each month, laboratory and imaging findings as well as family and individual history of atopy. We also discussed the use of inhaled medications, the need for extended diagnosis and accessory testing during infection.

Background/Objectives: Human breast milk is a biologically active fluid. It contains immune cells, stem cells, epithelial cells, and lactocytes. These components may support infant development and immune defense. While milk composition is known to vary with physiological and nutritional factors, the impact of the home environment remains poorly understood. The aim of this study was to examine how selected conditions affect the cellular composition of breast milk. Methods: We conducted a cross-sectional study involving 49 lactating mothers of healthy infants under 6 months of age. Breast milk samples were analyzed using flow cytometry. We measured proportions of immune cells (CD3⁺, CD4⁺, CD8⁺, CD19⁺, and CD16/56⁺), hematopoietic stem cells (CD34⁺), mesenchymal stem cells (CD105⁺, CD73⁺, and CD44⁺), and lactocytes (CD326⁺ CD73⁺ and CD326⁺ CD73⁻ phenotypes). Participants completed a questionnaire assessing number of children, co-sleeping, pet ownership, and number of household members. Results: Mothers with more than one child showed higher percentages of CD4⁺ (p = 0.047) and CD8⁺ (p = 0.031) T cells and fewer CD73⁺ lactocytes (p = 0.028). Co-sleeping was associated with lower levels of CD3⁺ T cells in milk (p = 0.021). Pet ownership correlated with a lower proportion of cytotoxic CD8⁺ cells (p = 0.048). The number of household members had no significant effect. Conclusions: Domestic factors such as number of children, co-sleeping, and pet exposure are associated with shifts in the immune and lactocyte cell composition of breast milk. These findings suggest that breast milk dynamically adapts to maternal and household-level immune stimuli.

Introduction and objective: Asthma is one of the most common chronic diseases in the paediatric population. The aim of this study was to evaluate selected biomarkers: fractional exhaled nitric oxide (FeNO), eosinophil count, periostin; and potential biomarkers: progranulin, matrix metalloproteinase-9 (MMP-9) and tumour necrosis factor alpha (TNFα) in the diagnosis of asthma in children. Materials and methods: The study group consisted of 25 children with atopic asthma in a stable period of the disease, aged 6–17 years. The control group consisted of 21 healthy children aged 6–18 years with no history of allergic diseases. Results: Significantly higher serum periostin levels were observed in children with asthma compared to the control group. There were no statistically significant differences in progranulin, periostin and MMP-9 levels between asthmatic children vs. healthy controls, or between patients with controlled vs. uncontrolled asthma. Children with uncontrolled asthma had significantly higher FeNO levels compared to children with controlled asthma. Exhaled FeNO levels were significantly higher in children with eosinophil levels above 0.3 × 103/µL than in those with eosinophil levels below 0.3 × 103/µL. Children with elevated FeNO had higher progranulin levels compared to children with normal FeNO values. There was a statistically significant positive correlation between FeNO and serum progranulin levels. Conclusions: Periostin may be used as a biomarker of atopic asthma in children. The applicability of FeNO and eosinophil count in the diagnosis of asthma in children has been confirmed. The role of progranulin and MMP-9 in the pathogenesis of asthma and their usefulness as a biomarker in children requires further study.

Infections with human herpesvirus type 6 commonly affect children up to 3 years of age. The infection is usually mild, however, severe cases involving the central nervous system can occur. We conducted a retrospective analysis of three cases who tested positive for human herpesvirus type 6 in cerebrospinal fluid polymerase chain reaction. Symptoms, laboratory findings, and proposed management in cases of uncertain aetiology of the neuroinfection are discussed. Attention is also drawn to the controversies related to the interpretation of molecular findings due to the latency of human herpesvirus type 6 infection and the lack of treatment recommendations for encephalitis of the aforementioned aetiology. Management of severe cases is suggested, along with potential treatment options.