Pneumocystis pneumonia (PP) is caused by Pneumocystis jirovecii (formerly P.carinii f. Sp. hominis) and is one of main opportunistic infections in AIDS patients.

The first cases of Pneumocystis pneumonia were detected in Europe during the Second World War. The disease mainly affected people suffering from immunodeficiency due to malignant tumors, immunosuppressive therapy, congenital immunodeficiency, etc. With the start of the AIDS epidemic in 1980, the incidence of PP has increased considerably. Thus, during the first years of the epidemic, it reached 20 cases per 100 people infected per year; PP accounted for 2/3 of all opportunistic AIDS infections, around 75% of those infected suffered from this disease once in their life.

The introduction into clinical practice of pneumocystis prophylaxis in 1989 resulted in a decrease in the incidence of PP in adults infected with HIV from 53% to 42% in 1992, and the use of combination antiretroviral therapy since 1992 led to an annual decrease of this indicator by another 3.4%. The introduction of highly active antiretroviral therapy (HAART) into clinical practice has also helped reduce the incidence of the disease, as well as other opportunistic infections. Thus, according to a cohort study in which more than 8,500 people infected with HIV participated, the incidence of PP rose from 4.9 cases per 100 people infected per year (until March 1995) to 0.3 case (after March 1998)..).

During the first years of the HIV epidemic, Pneumocystis pneumonia occurred in children infected with HIV with a frequency of 1.3 cases per 100 infected children per year, and this indicator for children in the first year life was significantly higher - 9.5 cases per 100 children per year. In the 1990s. Over the past century, the frequency of infections has decreased, mainly due to improved prenatal diagnosis and the conduct of preventive treatment for HIV infection. Since PP most often develops at 3 to 6 months of age, when HIV infection is often not yet detected, the use of HAART has a lesser effect on the incidence of infection in children.

In developing countries, despite the extremely high frequency of HIV infection and the lack of adequate preventive and therapeutic measures, the incidence rate of Pneumocystis pneumonia remains high. For example, a study in Thailand showed that the incidence of PP in people infected with HIV is 27 to 40%; in other studies, this indicator was 24-29%, depending on the population studied. However, there are a number of developing countries where the incidence of PP remains low, for example, Central African countries (0-11% of people infected with HIV).

Despite current preventive and therapeutic measures, even in developed countries, Pneumocystis pneumonia is the most common opportunistic infection in people infected with HIV. The reason for this is the emergence of resistant pneumocysts, as well as the low efficacy of preventive treatment in individuals with a small number of CD4 + cells. Studies have shown that a decrease in the concentration of CD4 + cells below 200 / μl is a major risk factor for the development of PP, regardless of the use of HAART, and the risk of infection. increases exponentially. The incidence of PP in children in a younger age group is less dependent on the number of CD4 + cells; In children over 6 years of age, a decrease in this indicator is considered, as in adults, as a risk factor for the development of PP and is an indication of preventive treatment.

According to some researchers, the decrease in the incidence of Pneumocystis pneumonia in developed countries may be short-lived. Not only does HIV infection become resistant to current treatment, but pneumocysts can also become resistant to drugs. The drug of choice for the prevention and treatment of PP is trimethoprim-sulfamethoxazole. A link has been demonstrated between the supply of sulfanilamide and mutations in the gene coding for the synthesis of dihydropteroate synthetase in P.jirovecii, which, according to some researchers, is a prerequisite for the formation of pneumocysts resistant to trimethoprim-sulfamethoxazole.

Another alarming fact is the identification of a number of healthy individuals during the PCR study of asymptomatic colonization by pneumocysts. Although colonization of healthy individuals is relatively rare, in individuals infected with HIV, this figure reaches 69%. The clinical significance of this phenomenon is unclear, however, the presence of colonization can increase the risk of PP, contribute to the spread of infection, and also lead to the development of an inflammatory process in the lungs.

All of the above indicates the need for further study of the epidemiology and mechanisms of pneumocystis pneumonia infection, as well as the development of effective means of prevention and treatment.