Previous studies have reported cough, fever, shortness of breath, muscle pain, tiredness, and headache as the main clinical characteristics of COVID-19 (
14,
15). Laboratory findings have shown that decreased lymphocyte counts, increased liver enzymes, and bilateral pneumonia are the common clinical signs of COVID-19 infection (
16). However, the probable differences in the clinical features of this infection in pediatric and adult patients are still not well understood. In the present study, a retrospective analysis of the clinical features in pediatric patients with COVID-19 infection compared with that of adult patients showed that the clinical symptoms (including fever and cough) were milder in pediatric patients. This is because the immune system responds less in pediatric patients than in adult patients.
Fever is a common symptom in patients with COVID-19; however, it is less severe in pediatric patients than in adults. Thus, the number of fever days was more among adults than among pediatric patients. Cough was more severe in adults than in pediatric patients. A study by Du et al. found that dry cough and fever were the most common clinical signs of COVID-19 in pediatric patients and were less severe than in adults (
12). This is because a lower inflammatory response to lung injuries causes milder clinical symptoms in pediatric patients than in adults (
12). In this study, there was no difference in the prevalence of diarrhea between pediatric patients and adults. Moreover, other studies have reported no significant difference in the incidence of diarrhea between pediatric and adult patients with COVID-19 (
12). In this study, no dizziness was observed in any of the pediatric patients; however, a large number of adults complained of dizziness. In another study, the rate of dizziness was higher in adults than in pediatric patients (
12). Dizziness is one of the symptoms of COVID-19 in adults (
17,
18). C-reactive protein levels were elevated in adult and pediatric patients, suggesting that SARS-CoV-2 caused inflammation. It has been reported that the number of lymphocytes decreases in patients with COVID-19, which is associated with the severity of the disease (
19). People who die from COVID-19 have been found to have extremely low lymphocyte counts (
20). The current study showed that lymphopenia is more common in adult patients with COVID-19 infection than in pediatric patients. In a study by Du et al., it was reported that although lymphopenia occurs in adult and pediatric patients, it is more common in adults (
12). The COVID-19 infection is more severe in adults than in pediatric patients, which may be because lymphopenia is more common in adults. In the present study, liver enzymes increased in adults and pediatric patients; however, no significant difference was observed between the two groups. Liver enzyme levels have been shown to increase in patients with COVID-19 infection, which can have devastating effects, especially in people with liver problems (
21). The Cr and BUN levels in pediatric patients and adults were normal.
This study was performed on pediatric patients with COVID-19 infection, and the clinical findings were evaluated. The results showed that pediatric patients with COVID-19 have milder clinical symptoms than adults. However, according to the laboratory findings, pediatric patients must be followed up as adults and use preventive protocols.