Pneumonia is infection of the lungs. Other lower respiratory tract infections seen in children are croup (laryngotracheobronchitis), bronchitis, and bronchiolitis.
Pneumonia results from direct inflammation of the lung tissue. Most commonly, it is the result of infections (bacterial, viral or fungal), but it can occur as a result of chemical injury (gastric acid/ aspiration of food/ hydrocarbon and lipoid pneumonia/ radiation induced pneumonia). The causative agent may reach the lung via the blood stream or from direct inhalation
The incidence of pneumonia in developing countries in children less than 5 years old is almost 30% with a high mortality rate.
Common causes of pneumonia
Newborns:group B Streptococcus (GBS), respiratory syncytial virus (RSV).
Viruses: parainfluenza viruses, influenza virus, adenovirus, and respiratory syncytial virus (RSV). cytomegalovirus
Atypical organisms: Chlamydia trachomatis, Ureaplasma urealyticum, and Pneumocystis carinii (PCP). PCP is especially seen in children with immunodeficiencies.
Bacterial: B. pertussis, Streptococcus pneumoniae, Haemophilus influenzae, Haemophilus influenzae, mycobacterial tuberculosis.
Viruses: parainfluenza viruses, influenza virus, adenovirus, and respiratory syncytial virus (RSV).
Atypical organisms: Mycoplasma pneumoniae.
Bacterial: Pneumococcus, mycobacterial tuberculosis.
Older children and adolescents:
Atypical organisms: Mycoplasma pneumoniae, Chlamydia trachomatis.
Bacterial: Pneumococcus, B. pertussis, mycobacterial tuberculosis.
Other rare causes of pneumonia:
Histoplasma capsulatum: It is found in nitrate rich soil from bird droppings and decaying wood. It is usually acquired as a result of inhalation of spores. The infection is usually asymptomatic; however, in infants and young children it may cause respiratory distress and hypoxemia.
Cryptococcus neoformans: is a common among pigeon breeders, seen in immunocompromised patients.
In older children, pneumonia may complicate common varicella infections