Histoplasmosis is a deep mycosis caused by the dimorphic yeast fungus Histoplasma capsulatum, which affects tissue macrophages of the lungs, liver, spleen, lymph nodes, skin and mucous membranes. Among the various forms of the disease, acute histoplasmosis of the lungs prevails, characterized by fever, chest pain, cough, weakness, lymphadenopathy, X-ray changes. In the diagnosis of histoplasmosis, cultural, microscopic, histological studies are used; serological reactions, allergic tests. Patients are prescribed antimycotic drugs (amphotericin B, meglumine sodium succinate, ketoconazole, etc.)
Histoplasmosis (Darling’s disease, reticuloendothelial cytoplasmosis) is a fungal disease that causes damage to the mononuclear phagocyte system and proceeds with limited or generalized manifestations. Disease is an endemic infection for the western and southern states of the United States, Central and South America, Africa; less common in Europe and Asia. Men suffer from histoplasmosis 2 times more often than women, children twice as often as adults.
According to the clinical course, histoplasmosis of the lungs, extrapulmonary histoplasmosis (skin, mucous membranes, central nervous system, etc.) are distinguished. organs) and disseminated histoplasmosis. The course of pulmonary form can be asymptomatic, acute (clinically pronounced) and chronic. An important factor determining the severity of the course and prognosis is the state of cellular immunity. Severe disseminated forms of Darling’s disease usually occur in children, the elderly, HIV-infected people, patients with leukemia and lymphomas.
Dimorphic fungus Histoplasma capsulatum, which is the causative agent of histoplasmosis, can exist in 2 forms: tissue (yeast) and mycelial (culture). In the human body, there is a tissue form of a microorganism that affects the cells of the organs of the reticuloendothelial system (liver, spleen, lymph nodes, etc.). The cultural form of the fungus develops outside the body, at temperatures below 30 °With and grows well on nutrient media. Histoplasmas persist for a long time in water and in moist soil; they quickly die under the influence of disinfectants.
The natural reservoir of the fungus is the soil contaminated with droppings and feces of infected animals and birds (bats, dogs, cats, chickens, pigeons, etc.). A favorable environment for the development of fungi are abandoned buildings and wells, caves, grottoes, hollows of old trees, air conditioners, etc. Human infection occurs by air-dust inhalation of fungal elements with dust particles, often during construction and excavation work. At risk for the incidence are rural residents, farmers, poultry farm workers, miners, geologists, tourists, cavers, etc. The transmission of histoplasmosis from animals to humans or from humans to humans is excluded.
In most cases, the entrance gate of infection is the respiratory tract. Once in the bronchi and alveoli, histoplasm spores turn into a tissue form and cause the development of a primary focus in the lungs and regional lymph nodes. In the lung tissue, a granulomatous process develops with the outcome of necrosis, ulceration or calcification, less often abscessing. Acute pulmonary histoplasmosis is similar in its pathogenesis to primary pulmonary tuberculosis. Getting into the systemic bloodstream, histoplasmas cause sensitization of the body and the production of specific antibodies. Sometimes the pathological process is limited to this, which corresponds to the subclinical form of histoplasmosis. In other cases, the hematogenic spread of fungal infection causes the development of disseminated histoplasmosis.
Due to the aerogenic route of infection, the pulmonary form prevails in the clinic of histoplasmosis. Primary extrapulmonary forms of Darling’s disease are rare; usually lesions of the skin, mucous membranes, and intestines are manifestations of disseminated histoplasmosis. The incubation period lasts on average 7-14 days, sometimes less or longer (from 4 to 30 days).
In 80% of infected patients, acute histoplasmosis of the lungs has an asymptomatic course, detected by positive results of intradermal tests with histoplasmin, serological reactions, X-ray changes in the lungs. With a mild course of histoplasmosis, the well-being of patients practically does not suffer; occasionally short-term fever, catarrh of the upper respiratory tract, cough, which are stopped within a week. For severe forms of pulmonary histoplasmosis, a sudden onset, high fever (up to 40-41 °) is typicalC) with significant daily temperature changes; change of chills by diffuse sweating; severe headache, ossalgia and myalgia. Chest pains, cough with purulent sputum, hemoptysis are characteristic; nausea, diarrhea, abdominal pain are possible. The febrile period lasts from 2 to 6 weeks, after which a prolonged stage of convalescence occurs, occurring with subfebrility, asthenization, and decreased ability to work.
The chronic form of histoplasmosis of the lungs has a long progressive course. It is characterized by moderate fever, cough with sputum, X-ray changes (cavities, fibrosis, multiple calcifications in the lung tissue). Histoplasmosis is often combined with sarcoidosis, tuberculosis, leukemia, reticulosis.
With the development of acute disseminated histoplasmosis against the background of fever and severe general intoxication, multiple secondary foci of fungal infection occur in various organs. The lesion of the skin and mucous membranes can be manifested by various rashes (maculopapular, hemorrhagic, furuncle-like rash, erythema), ulcerative stomatitis and pharyngitis, abscesses of subcutaneous tissue, ulcers of the external genitals, cracks of the anus. Among other organ manifestations of disseminated histoplasmosis, lymphadenopathy, meningoencephalitis, retinitis, chorioiditis, pericarditis, infectious endocarditis, ulcerative colitis, hepatosplenomegaly, mesadenitis, peritonitis can occur. The course of chronic disseminated histoplasmosis is more erased and sluggish, but inevitably leads to multiple organ lesions.
The course of histoplasmosis has its own characteristics in young children and HIV-infected people – in these cases, the disease develops as a disseminated process. Children have pronounced hepatolienal syndrome, generalized lymphadenopathy, lung, skin and intestinal lesions. HIV-infected persons suffer from histoplasmosis in about 0.5% of cases, i.e. less often than candidiasis or aspergillosis. The clinical and radiological picture is characterized by lymphadenopathy, high fever, significant hepatosplenomegaly, cough and infiltrates in the lungs. Mortality from histoplasmosis in this category of patients reaches 80%.
Recognition of histoplasmosis is not an easy task for infectious disease specialists, pulmonologists and other specialists to whom patients can turn. The diagnosis is confirmed by the release of Histoplasma capsulatum from sputum, bronchial lavage; in disseminated form – from blood, urine, feces, abscess contents, sternal punctate, cerebrospinal fluid. In favor of histoplasmosis, the receipt of a mushroom culture when sowing these materials on nutrient media testifies. For the diagnosis of histoplasmosis, serological reactions (RSC, precipitation reaction and latex agglutination), biopsy of the bronchus, lymph nodes, and the edges of ulcers are also used, followed by histological examination. A highly specific test is an intradermal test with histoplasmin.
Radiography of the lungs in the acute stage of pulmonary histoplasmosis reveals large- and medium-focal infiltrates. In the future, foci of fibrosis and calcification form on the site of infiltrates. If acute pulmonary form is suspected, acute respiratory viral infections, bacterial pneumonia, atypical pneumonia, ornithosis, Ku fever, mycoplasmosis, tuberculosis are excluded. Chronic form of the lungs requires differentiation with pulmonary forms of deep mycoses (nocardiosis, aspergillosis, coccidioidomycosis, blastomycosis), lymphogranulomatosis. Disseminated forms of mycosis should be distinguished from sepsis and miliary tuberculosis.
People with asymptomatic or acute localized form of histoplasmosis usually do not receive antifungal treatment. In these cases, they are limited to symptomatic therapy and general restorative measures. With prolonged or severe forms of histoplasmosis, the appointment of antimycotic drugs – itraconazole, ketoconazole, amphotericin B, meglumine sodium succinate is indicated. Along with the systemic use of antimycotics, it is advisable to carry out medicinal inhalations. Additionally, vitamins, antihistamines, and proper nutrition are recommended. With the development of complications of histoplasmosis, surgical treatment may be required (pericardial puncture, removal of lymph nodes, lung resection, prosthetics of heart valves, etc.).
Acute histoplasmosis of the lungs often proceeds in an asymptomatic form and usually ends favorably for the patient. Long-term consequences of chronic histoplasmosis may be pulmonary fibrosis, arthritis, erythema nodosum, uveitis, encephalopathy, seizures, heart failure. Disseminated forms pose the greatest threat to children, the elderly, and patients with HIV infection. Nonspecific prevention of histoplasmosis should include disinfection of the soil, reduction of dustiness of the air, the use of respirators during excavation.