The role of eosinophil cationic protein in patients with Mycoplasma pneumoniae infection.

BACKGROUND To study the role played by eosinophil cationic protein (ECP) in patients with Mycoplasma pneumonia infection. METHODS Pediatric patients aged 4 to 14 years old were divided into 3 groups, each consisting of 30 patients. Group 1 comprised patients with known M. pneumoniae infection. Group 2 comprised patients with asthma who were in a stable condition with no infection, acute asthma exacerbation or steroid use in the last 2 months. Group 3 consisted of healthy children and was designated the control group. The level of ECP in patients' serum was measured by an ECP radioimmunoassay kit. RESULTS There were 90 children enrolled in this study; 59 (65.56%) were boys and 31 (34.44%) were girls. Mean serum ECP levels between males and females was not significantly different (p = 0.544). The variance of serum ECP levels decreased as patient age increased, but there was no relationship between serum ECP level and patient age (gamma = 0.118, p = 0.267). Serum ECP levels were similar in both the M. pneumoniae-infected and asthma groups; serum ECP levels in the control group were less than the levels seen in the other 2 groups. The difference in serum ECP levels among the 3 groups was statistically significant (p < 0.001). CONCLUSION Both the children who had M. pneumoniae infection and the children with asthma had significantly increased serum ECP levels compared to normal healthy children. The elevated ECP levels found in the serum of patients with M. pneumoniae infection may be associated with damage to the respiratory epithelium and accelerated hypersensitivity in the respiratory system. Decreasing the serum level of ECP may potentially be a method of relieving symptoms in patients with M. pneumoniae infection. Additional studies are warranted to further validate this conclusion.