DEFINITIONS AND EPIDEMIOLOGY
A child presenting with recurrent respiratory infections or radiographic abnormalities poses a common diagnostic problem for general pediatricians and pulmonary specialists alike. Pneumonia can be described in both clinical and radiographic terms. The World Health Organization (WHO) defines pneumonia clinically as cough or dyspnea in association with labored breathing or tachypnea, and radiographically as an opacity occupying at least part of a single lobe and up to the entire lung.1,2 The incidence of pneumonia in developed countries is approximately 3–3.6 children per 100, whereas in developing countries, it can reach as high as 40 per 100 children.3 Recurrent pneumonia has been defined as two episodes in 1 year or three in a lifetime, with radiographic clearing between episodes.4 It should be differentiated from persistent pneumonia, which is defined as continuation of symptoms and radiologic changes for 6 weeks or more despite treatment.5 While the incidence of recurrent pneumonia among large populations of children is unknown, a retrospective cohort study of approximately 30,000 German children aged 5–7 years estimated the prevalence of recurrent pneumonia, defined as three or more episodes in a lifetime, to be 7.7%.6
Several series have described the frequency and leading causes of recurrent pneumonia. These studies demonstrate that most children with recurrent pneumonia have an identifiable cause for their recurring symptoms. The most common cause, however, varies with the characteristics of the population of children studied, whether inpatient or outpatient, referred to a subspecialty or general pediatric service, or from developed or developing countries. In a 10-year review of hospital records at a tertiary care children’s hospital in Canada, 238 (8%) of 2952 children with pneumonia met criteria for recurrent pneumonia (twice in one year or at least three episodes during their lifetime); 92% of the children with recurrent pneumonia had an identifiable underlying cause.7 These included oropharyngeal incoordination with aspiration (48%), immune disorders (10%), congenital cardiac defects (9%), asthma (8%), pulmonary anomalies (8%), gastroesophageal reflux (5%), and sickle cell disease (4%). Similarly, Ciftci et al.8 reviewed all children admitted to the pediatric infectious disease service of a tertiary care hospital in Turkey. Children without radiographic diagnostic confirmation were excluded from analysis, as were those with cystic fibrosis or congenital heart disease. Nine percent of 288 patients met the criteria and underlying disease was identified in 85% of patients. While the proportion of children with recurrent pneumonia and those with identified underlying causes were similar in both studies, the frequency of etiologies was different; in the latter study asthma occurred in 32% and swallowing dysfunction was present in only 3%.
Among those children with recurrent pneumonia evaluated on an outpatient basis, the majority also have an identified underlying cause. Lodha et al9 reviewed all children presenting to a pediatric pulmonary clinic in New Delhi, India, in a 4-year period. Children who met clinical criteria and had radiographic confirmation of pneumonia were included; ...