Pneumocystis carinii pneumonia, also known as Pneumocystis jirovecii pneumonia or interstitial plasma cell pneumonia, is a rare type of pneumonia that primarily occurs in immunocompromised children.

bubble_chart Etiology

The pathogen is Pneumocystis carinii, which exists in trophozoite and cyst forms, primarily residing in the lungs. Pneumocystis belongs to the fungal category. Pneumocystis carinii cysticercosis is mainly observed in five types of patients:

1. premature infants and newborns;
2. children with congenital immunodeficiency or secondary immunosuppression;
3. individuals with malignant tumors such as leukemia, lymphoma, and other tumor diseases;
4. children undergoing immunosuppressive therapy after organ transplantation;
5. children with AIDS.

bubble_chart Clinical Manifestations

1. Infantile type: Mainly occurs in infants aged 1 to 6 months, classified as interstitial plasma cell pneumonia. The onset is gradual, with primary symptoms including poor feeding, dysphoria, cough, increased respiratory rate, and cyanosis, while fever is not prominent. Few rales are heard during auscultation, and respiratory distress gradually worsens within 1–2 weeks. A notable characteristic of this disease is the disproportion between the scarcity of lung signs and the severity of respiratory distress symptoms. The course lasts 4–6 weeks, and without treatment, approximately 25–50% of affected infants die.
2. Childhood type: Primarily occurs in children with compromised immune function due to various causes. The onset is abrupt, differing from the infantile type in that nearly all patients exhibit fever. Additionally, common symptoms include rapid breathing, cough, cyanosis, retractions, nasal flaring, and diarrhea. The disease progresses rapidly, often leading to death if untreated.

bubble_chart Auxiliary Examination

1. White blood cell count: Normal or slightly elevated, with approximately half of cases showing lymphocytopenia and grade I eosinophilia.
2. Blood gas analysis: Reveals significant hypoxemia and an increased alveolar-arterial oxygen gradient. Pulmonary function tests demonstrate progressive deterioration.
3. X-ray examination: Shows bilateral diffuse granular shadows extending from the hilar regions to the periphery, presenting with a ground-glass appearance accompanied by air bronchograms. These later develop into dense linear opacities interspersed with irregular patchy shadows. In the late stage (third stage), persistent pulmonary interstitial emphysema becomes evident, particularly in the peripheral lung regions. May be accompanied by mediastinal emphysema and pneumothorax.
4. Bronchoalveolar lavage and transbronchial lung biopsy: Detection rate of cysts can reach 90%.

bubble_chart Treatment Measures

1. Pathogenic treatment.
2. Supportive therapy: including intramuscular injection of gamma globulin or placental globulin to enhance immunity. Oxygen therapy is administered if necessary. If this disease occurs during the use of adrenal corticosteroids, the dosage should be reduced or discontinued. To prevent cross-infection of this disease in high-risk children, recent recommendations advocate for respiratory isolation until the treatment is completed.