Pneumonia is an infection of the lower respiratory tract.
The annual incidence of pneumonia in children younger than 5 years is about 34 to 40 cases per 1000,
and decreases to 7 cases per 1000 in adolescents 12 to 15 years of age  .
Childhood mortality from pneumonia in developed countries is low,
instead pneumonia represents the main cause of childhood mortality in developing countries .
mortality from respiratory infections increases in immunocompromised pediatric patients.
In a paper by Zengin et al,
infections were listed among the most important causes of mortality in pediatric patients: more in detail,
setticemia and pneumonia represented the causes of death .
A large number of etiologic agents causes lung inflammatory processes in immunocompromised children,
protozoa and helminths.
Among fungal infections,
most common pathogens are: Aspergillus fumigatus,
Main viral pathogens are Cytomegalovirus,
Varicella zoster and Influenza Virus.
The incidence of pneumonia caused by bacterial (especially Mycobacterium TB),
helminth or protozoal infection is lower.
The etiological diagnosis is difficult to be identified,
because in most cases radiological features of lung infection caused by different microorganism are quite similar.
Several diseases may induce an immunocompromised status in children: in our clinical-radiological database,
the most frequent encountered diseases were: acute myelogeneous leukemia,
acute lymphoblastic leukemia,
Clinical management may be difficult in these patients: during autologous or allogenic stem cell transplantation,
patients may reach a severe immunodepression status,
and may be at risk for many infections.
As reported in the paper by Demirkazik et al,
patients during treatment may develop neutropenic fever,
and thoracic imaging is generally required to investigate the presence of pulmonary infections .
Chest X-ray is generally adopted as first-line imaging modality; however,
it has limited sensitivity and specificity.
HRCT - due to its great diagnostic accuracy - is very often required in these neutropenic pediatric patients with fever,
in order to:
- exclude a pulmonary infection not reliable/misdiagnosed on chest X-ray;
- better investigate aspecific infiltrated depicted on chest X-ray (HRCT findings could be suggest a specific diagnosis to radiologists).
As already reported in literature ,
chest HRCT plays an important role in the assessment of respiratory infections of children in some specific situations:
- to exclude a possible malformation in children with recurrent infections;
- in cases with pulmonary or pleural complications;
- in immunocompromised patients;
- to guide an interventional procedure;
- in monitoring sequelae of diseases .
HRCT is accurate in the interpretation of thoracic diseases due to infections: in a previous study by Beyramoglu et al,
HRCT demonstrated a greater diagnostic accuracy than chest radiography in a population of children having recurrent respiratory infections .
More in detail,
HRCT was able to detect the underlying pathology and the pulmonary sequelae in 22 out of 51 patients,
adding more information than chest radiography.
Exposure to ionizing radiations should be considered by clinicans and radiologists,
reminding the differences listed in Table 1.