Pneumocystosis is an opportunistic infection of the respiratory tract, more often affecting young children, as well as people with weakened immunity. Pneumocystosis can occur in the form of acute respiratory infections, laryngitis, obstructive bronchitis, exacerbation of CLD, interstitial pneumonia. Diagnosis of pneumocystosis is based on the detection of pneumocysts in sputum and bronchial secretions using microscopy and PCR; histological examination of bronchial biopsies; radiography and CT of the lungs, scintigraphy, spirography. For anti-pneumocystic therapy, drugs sulfamethoxazole + trimethoprim, pentamidine, a combination of trimethoprim with dapsone and other treatment regimens are used.
Pneumocystosis is a pulmonary invasion caused by pneumocysts and occurring mainly in the form of pneumocystic pneumonia. Pneumocystosis is an immunodeficiency-associated infectious disease, which most often affects premature infants, as well as patients with primary and secondary immunodeficiency. Pneumocystosis is a deadly danger for HIV/AIDS patients: in the absence of treatment, the disease inevitably ends in death. Pneumocystosis can occur as a sporadic or nosocomial infection in the departments of pediatrics, hemoblastosis, pulmonology, tuberculosis infectious hospitals.
To date, the issue of the specific identity of the causative agent of pneumocystosis has not been finally resolved. For a long time, the microorganism Pneumocystis Carinii was attributed to the simplest class of spores. However, currently the dominant view is that pneumocysts occupy an intermediate position between lower and higher fungi. In their development, pneumocysts undergo 4 stages: trophozoitis, precysts, cysts and sporozoitis occurring on alveocytes. When the shell of a mature cyst ruptures, sporozoites come out of it, which penetrate into the pulmonary alveoli, triggering the next cycle of the stage development of pneumocysts of a new generation.
The source of epidemiological danger is an invasive person (patient or carrier), which secretes sporozoites with mucus particles into the external environment when coughing or sneezing. Transmission of pathogens of pneumocystosis occurs by aspiration mechanism, airborne droplets, airborne dust, inhalation or aerogenic pathways. It is believed that up to 10% of clinically healthy individuals are carriers of pneumocysts, but in people with a normally functioning immune system, the invasion is asymptomatic. Premature newborns, children with hypogammaglobulinemia, hypotrophy, rickets, patients with HIV/AIDS and tuberculosis, patients receiving immunosuppressive therapy for collagenoses, malignant neoplasms, hematological and lymphoproliferative diseases, organ transplantation, etc. are mainly at risk of morbidity with manifest forms of pneumocystosis.
Pneumocystosis develops with a decrease in the number of CD4+ cells (T helper cells) by 4 or more times compared to the norm and reaching a level of less than 200 cells in 1 µl. In violation of cellular and humoral immunity, pneumocysts begin to actively multiply in the alveoli, causing the development of reactive alveolitis, the formation of foamy alveolar exudate containing pneumocysts, leukocytes, cellular detritus and fibrin. With the progression of the pathological process, there are areas of atelectasis in the lungs, bullous swelling of the lung tissue, which is accompanied by a violation of ventilation and gas exchange, the development of respiratory failure.
In the clinical course of pneumocystosis, edematous (1-7 weeks), atelectatic (about 4 weeks) and emphysematous stages are distinguished. In some patients, pneumocystosis can occur in the form of laryngitis, obstructive or asthmatic bronchitis, bronchiolitis; in other cases, pneumocystic pneumonia develops.
The incubation period of pneumocystosis takes from 10 days to 2-5 weeks. Manifestations of the edematous stage develop gradually and in the early stages include subfebrility, weakness, lethargy. At the end of the first period, dry cough, tachypnea, shortness of breath joins. Signs of developing pneumocystosis in infants can be sluggish sucking, refusal to feed, poor weight gain, cyanosis of the nasolabial triangle. There are no radiological changes in the lungs in the edematous stage of pneumocystosis; harsh breathing, small- and medium-bubbly wheezing are determined auscultatively; percussion – tympanitis in the upper chest.
In the atelectatic stage of pneumocystosis, fever reaches febrile values; an obsessive whooping cough with foamy sputum appears; shortness of breath occurs with minimal exertion. Objectively, constant cyanosis, tachypnea, tachycardia, increased intercostal spaces, weakened breathing, small-bubbly wheezing are detected. Lung x-ray determines the signs of pneumocystis pneumonia – infiltrates of heterogeneous density and atelectasis (so-called “cotton lungs”). In immunocompromised individuals, in addition to interstitial pneumonia, extrapulmonary manifestations of pneumocystosis in the form of pneumocystic retinitis, thyroiditis, otitis, mastoiditis or sinusitis are possible.
In the atelectatic stage, pneumocystosis can be complicated by the development of pneumothorax, exudative pleurisy, pulmonary heart, pulmonary edema, and in the case of bacterial or fungal infection, lung abscess. Deaths during this period are usually caused by respiratory and heart failure. The third, emphysematous stage of pneumocystosis is characterized by a decrease in shortness of breath and an improvement in the general condition of patients. In the outcome of pneumocystosis, emphysema of the lungs develops, accompanied by a significant decrease in the indicators of the function of external respiration.
Clinical, physical and radiological data for pneumocystosis are not pathognomonic, which makes it difficult to diagnose the disease in a timely manner. Meanwhile, pneumocystis pneumonia should always be excluded in immunocompromised patients. In order to verify pneumocystosis, a complex of laboratory and instrumental studies is carried out.
On radiographs and CT scans of the lungs, in typical cases, an oblacoid decrease in the transparency of the pulmonary fields, called “snow flakes” or “cotton lung”, is determined. Sometimes radiological changes are absent or have an atypical picture. With the help of FER, signs of respiratory insufficiency of the restrictive type are detected; a study of the gas composition of the blood indicates hypoxemia.
To confirm the diagnosis of pneumocystosis, bronchoscopy with bronchial secretion sampling, a trans-bronchial lung biopsy, lung scintigraphy with gallium-67 is performed. For laboratory detection of P.carinii, stained sputum smears, bronchial and tracheal aspirate are microscopically examined; histological examination of biopsies, sputum examination by PCR is performed. Immunological diagnostics is carried out: determination of the titer of anti-pneumocystic IgG and IgM in blood serum using IFR and ELISA. Differential diagnosis of pneumocystosis should be carried out with cytomegalovirus, chlamydia, ureaplasma, bacterial pneumonia, pulmonary tuberculosis, Kaposi’s sarcoma, etc.
Treatment of pneumocystosis is carried out in a hospital. Persons with immunodeficiency and premature infants should be placed in separate sterile wards with laminar airflow. In most cases, combined drugs (sulfamethoxazole + trimethoprim, trimethoprim + dapsone), pentamidine, eflornitine, atovaquone for 2-3 weeks are used for specific pharmacotherapy of pneumocystosis. To eliminate the side effects of therapy, folic acid and glucocorticoids are prescribed. Infusion therapy is performed (administration of gamma globulin, saline solutions, glucose, blood plasma, albumin, etc.), oxygen therapy. In patients with HIV infection, etiotropic therapy of pneumocystis pneumonia is combined with highly active antiretroviral therapy.
The survival rate for pneumocystosis is 75-90%, and with the repeated development of pneumocystic pneumonia – 60%. 25-60% of HIV-infected people have relapses of the disease during the year, so patients need an anti-relapse course of chemotherapy.