Pneumocystis jirovecii Pneumonia in Children

Pneumocystis jirovecii (previously known as Pneumocystis carinii), a yeast-like, atypical fungus, is an important human pathogen especially in the immunocompromised hosts. It primarily causes pneumonia (P. jirovecii pneumonia or PJP), but rarely can infect other extrapulmonary sites, such as lymph nodes, spleen, liver, and bone marrow. Though an early age of colonization/infection has been documented even in healthy children, children with human immunodeficiency virus (HIV) infection, those with immuno-suppression secondary to malignancies, cancer chemotherapy, and other immunosuppressive agents, and primary immunodeficiency are the ones primarily affected with the disease. The mode of presentation is variable depending on the underlying disease, immune status, and age of the patient, but clinical features of PJP are largely nonspecific. Though diffuse, perihilar predominant, bilaterally symmetrical interstitial infiltrates with apical sparing is characteristically seen in pulmonary imaging, it is very difficult to differentiate between PJP and other causes of pneumonia in immuno-compromised hosts. The growth of the organism being extremely difficult in the laboratory, direct demonstration of the organism or its DNA in pulmonary secretions (induced sputum, bronchoalveolar lavage [BAL], etc.) by either direct stains or polymerase chain reaction (PCR) is the predominant mode of diagnosis. Chemoprophylaxis is indicated for HIV-infected infants and other children with profound immunosuppression. Cotrimoxazole is the drug of choice for both prophylaxis and therapy in children with PJP; pentamidine, atovaquone, dapsone, and clindamycin/primaquine are other alternatives. Following the advent of highly active antiretroviral therapy (HAART) for the treatment of HIV disease and co-trimoxazole prophylaxis, both the incidence of PJP and associated mortality have decreased dramatically in the developing regions. Developing countries still have very high morbidity and mortality with PJP, especially in HIV-infected children.