Pneumocystis Jiroveci (Previously Known as Pneumocystis Carinii Pneumonia)
Basics
DESCRIPTION
Opportunistic lung infection caused by Pneumocystis jiroveci. This organism is currently considered a primitive fungus based on DNA sequence analysis. It has two developmental forms (the cysts contain sporozoites that become trophozoites when excised).
- Although previously known as Pneumocystis carinii pneumonia (PCP), the acronym PCP is still in use and refers to Pneumocystis pneumonia.
- PCP occurs almost exclusively in the immunocompromised host.
- PCP is an AIDS-defining illness. It is the most common opportunistic life-threatening lung infection in infants with perinatally acquired HIV disease.
- P. jiroveci causes a diffuse pneumonitis characterized by fever, dyspnea at rest, tachypnea, hypoxemia, nonproductive cough, and bilateral diffuse infiltrates in the roentgenogram. It is a severe condition frequently leading to respiratory failure, necessitating intubation and mechanical ventilation.
- Chemoprophylaxis against this microorganism has proven successful. Therefore, early identification of the HIV-infected mother becomes essential.
- Despite advances in therapy, the infection continues to be associated with significant morbidity and mortality.
EPIDEMIOLOGY
- Ubiquitous in mammals worldwide, particularly rodents
- Growth on respiratory tract surfaces
- Mode of transmission is unknown:
- Airborne person-to-person transmission is possible, but case contacts are rarely identified.
- Environmentally acquired
- Asymptomatic infection appears early in life; >70% of healthy individuals have antibodies by age 4 years.
- Primary infection is likely to be the mechanism in infants. Reactivation of latent disease with immunosuppression was proposed as an explanation for disease later in childhood; however, animal models of PCP do not support this proposition.
- PCP in the HIV patient can occur at any time but usually presents during the 1st year of life. The highest incidence is between 3 and 6 months of age.
RISK-FACTORS
Immunocompromised host
- Children with congenital or acquired AIDS and recipients of suppressive therapy in the treatment of malignancies or after organ transplantation are at high risk.
- In leukemic patients, the incidence of PCP has been directly related to the degree of immunodeficiency resulting from chemotherapy.
- Epidemics of PCP were reported in premature and malnourished infants and children in resource-limited countries and during times of famine.
GENERAL-PREVENTION
- Chemoprophylaxis indications: During high-risk periods, PCP can be effectively prevented in the immunodeficient host by chemoprophylaxis in the following groups:
- HIV exposed: 4 to 6 weeks to 4 months
- HIV infected or indeterminate: 4 to 12 months
- HIV infected: 1 to 5 years if CD4+ T-lymphocyte count is <500 cells/μL or <15%
- HIV infected: ≥6 years if CD4+ T-lymphocyte count is <200 cells/μL or <15%
- Severely symptomatic HIV patients or those with rapidly declining CD4 counts
- HIV patients who have had previous PCP illness
- Children who have received hematopoietic stem cell transplants (HSCTs)
- All HSCT recipients with hematologic malignancies (e.g., leukemia, lymphoma)
- All HSCT recipients receiving intense conditioning regimens or graft manipulation
- Prophylaxis is initiated at engraftment and administered for 6 months; longer than 6 months in children receiving immunosuppressive therapy or with chronic graft-versus-host disease
- Drug regimen for prophylaxis
- Trimethoprim-sulfamethoxazole (TMP-SMX) is the drug of choice.
- 150 mg/m2 body surface area per day of TMP or 750 mg/m2 body surface area per day of SMX PO divided into 2 doses on 3 consecutive days per week
- TMP-SMX can also be given 7 days a week when prevention against other bacterial infections is sought.
- For patients who cannot tolerate TMP-SMX
- Dapsone (>1 month of age): 2 mg/kg (maximum 100 mg) PO daily or 4 mg/kg (maximum 200 mg) PO weekly
- Aerosolized pentamidine (>5 years of age): 300 mg via Respirgard II nebulizer inhaled monthly
- Atovaquone at age 1 to 3 months and >24 months: 30 mg/kg (maximum 1,500 mg/dose) PO daily; at age 4 to 24 months: 45 mg/kg (maximum 1,500 mg/dose) PO daily
- Trimethoprim-sulfamethoxazole (TMP-SMX) is the drug of choice.
PATHOPHYSIOLOGY
- In the immunodeficient child, the pathologic changes occur predominantly in the alveoli. Cysts and trophozoites are seen adhering to the alveolar lining cells or in the cytoplasm of macrophages.
- As infection progresses, the alveolar spaces are filled with a pink, foamy exudate containing fibrin, abundant desquamative cells, and a large number of organisms. Alveolar septal thickening with mononuclear cell infiltration is also seen.
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Citation
Cabana, Michael D., editor. "Pneumocystis Jiroveci (Previously Known as Pneumocystis Carinii Pneumonia)." Select 5-Minute Pediatrics Topics, 7th ed., Wolters Kluwer Health, 2015. Medicine Central, im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14034/all/Pneumocystis_Jiroveci__Previously_Known_as_Pneumocystis_Carinii_Pneumonia_.
Pneumocystis Jiroveci (Previously Known as Pneumocystis Carinii Pneumonia). In: Cabana MDM, ed. Select 5-Minute Pediatrics Topics. Wolters Kluwer Health; 2015. https://im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14034/all/Pneumocystis_Jiroveci__Previously_Known_as_Pneumocystis_Carinii_Pneumonia_. Accessed November 12, 2024.
Pneumocystis Jiroveci (Previously Known as Pneumocystis Carinii Pneumonia). (2015). In Cabana, M. D. (Ed.), Select 5-Minute Pediatrics Topics (7th ed.). Wolters Kluwer Health. https://im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14034/all/Pneumocystis_Jiroveci__Previously_Known_as_Pneumocystis_Carinii_Pneumonia_
Pneumocystis Jiroveci (Previously Known as Pneumocystis Carinii Pneumonia) [Internet]. In: Cabana MDM, editors. Select 5-Minute Pediatrics Topics. Wolters Kluwer Health; 2015. [cited 2024 November 12]. Available from: https://im.unboundmedicine.com/medicine/view/Select-5-Minute-Pediatric-Consult/14034/all/Pneumocystis_Jiroveci__Previously_Known_as_Pneumocystis_Carinii_Pneumonia_.
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