Pulmonary mucormycosis is a severe fungal disease that occurs mainly in immunocompromised individuals and is characterized by the development of vascular thrombosis and necrosis of the lung tissue. The main symptoms of the disease are nonspecific: they include fever, shortness of breath, cough and hemoptysis. The diagnosis is established on the basis of radiological or CT signs of lung damage, detection of zygomycetes in sputum, bronchial lavage waters, and other pathological material. The treatment combines the use of antimycotic drugs with surgical removal of necrotic tissues.
B46.0 Pulmonary mucormycosis
Mucormycosis (zygomycosis, mucorosis, phycomycosis) of the lungs is an opportunistic infection and ranks third among other invasive mycoses of the respiratory system. The incidence of all forms of mucormycosis is about 0.17 per 100 thousand population. Middle-aged men (65%) are more likely to get sick. Lung damage is observed in 25% of all cases. The infectious process occurs in patients with severe disorders of the immune system. The pulmonary form of the disease is usually found in oncological and hematological patients, as well as in recipients of red bone marrow. Pulmonary mucormycosis is characterized by high mortality (50%- 80%).
Pulmonary mucormycosis causes
The causative agent of the disease is a number of families of lower fungi of the class Zygomycetes, of the order Mucorales. They are widespread everywhere, populate the air and soil. Representatives of this class belong to saprophages. They can be found in spoiled grain, some other products of animal and vegetable origin. Micromycetes grow very quickly and form small (about 6.6 microns) spores. Infection of a person with the subsequent occurrence of a pulmonary form of mycosis occurs aerogenically. In addition, infection is possible when eating foods spoiled by mushrooms, as well as by contact when performing medical manipulations, tattooing.
People with immunodeficiency are susceptible to the disease. Pulmonary mucormycosis occurs mainly in patients with a low number of blood neutrophils. Deficiency of these cells develops in cancer patients receiving chemotherapy, as well as against the background of long-term treatment with corticosteroids. Neutropenia is observed in patients suffering from hemoblastosis, in recipients of internal organs and bone marrow. Zygomycetes are resistant to a number of antifungal drugs and provoke the development of the disease against the background of preventive administration of these drugs. Cases of the pulmonary form of the disease have been reported in persons taking deferoxamine. Occasionally, lung mucormycosis occurs in patients with diabetes mellitus.
The mechanism of the disease development is not fully understood. It is known that a normally functioning immune system ensures the destruction and phagocytosis of zygomycetes trapped in the body with the help of neutrophils and alveolar macrophages. The acid-base balance of the blood serum performs certain protective functions. Hyperglycemia and ketoacidosis reduce the phagocytic activity of neutrophils, and prolonged treatment with corticoid hormones affects the barrier function of bronchoalveolar macrophages. Deferoxamine participates in the vital processes of some families of zygomycetes, provoking the development of a pathological process in patients receiving this drug.
Zygomycete spores enter the respiratory tract by aerogenic, hematogenic or lymphogenic pathways. They have a tropicity to the arterial endothelium. In the presence of favorable conditions, fungal conidia attach to the inner lining of the arteries, germinate it, damage endothelial cells and spread through the vascular bed. Thrombosis occurs. Due to a violation of the blood supply, necrotic changes develop in the corresponding areas of the lung tissue.
Pulmonary mucormycosis symptoms
Pulmonary phycomycosis has no pathognomonic clinical manifestations. The onset of the disease is similar to the debut of another severe infectious and inflammatory process of the respiratory tract. The first symptoms of the disease are dry unproductive cough and febrile or hyperthermic fever (body temperature rises above 38 ° C). Later, the cough becomes unproductive. There may be an admixture of blood in the sputum. The progression of mucormycosis often causes pulmonary bleeding.
Shortness of breath occurs with little physical exertion and at rest. Inhaling and exhaling are difficult, there is a feeling of lack of air. When the bronchi are affected, bronchial obstruction syndrome develops, characterized by expiratory shortness of breath and wheezing on exhalation. When the pleura is involved in the pathological process, intense chest pains appear, which increase with deep breathing. The patient’s condition progressively worsens against the background of treatment with broad-spectrum antibiotics.
Untimely diagnosed pulmonary mucormycosis in the absence of etiotropic therapy leads to severe complications. When the mycelium of fungi germinates large vessels, massive pulmonary bleeding occurs, which leads to the death of the patient. Another serious complication is the further spread of zygomycetes in the body. First, the pericardium, mediastinum, thorax are affected, later – other organs. Mycosis is disseminated. Mortality in this form of pathology is about 95%. Accurate diagnosis and correct therapeutic tactics of zygomycosis can reduce the mortality rate by up to 50%. After recovery, large areas of pulmonary fibrosis and pleural fusion often remain, leading to the development of respiratory failure.
Early detection of pathology increases the patient’s chances of a favorable outcome. However, it is difficult to diagnose pulmonary mucormycosis due to the similarity of the clinical picture and radiological manifestations with the symptoms of pulmonary forms of aspergillosis and candidiasis. Infectious diseases specialists and pulmonologists are engaged in diagnostic search. Atypically occurring, insensitive to antibacterial therapy, severe pneumonia on the background of immunodeficiency gives grounds to assume zygomycosis. The final diagnosis is established by:
- Methods of radiation diagnostics (lung x-ray, chest CT). Radiological symptoms are identical to signs of lung aspergillosis. On radiographs, spherical infiltrates of different sizes with the presence of a sickle-shaped enlightenment zone are determined. Computed tomography allows you to identify the “halo symptom” – the presence of areas of lung tissue in the form of frosted glass. The rapid progression of the pathological process is characterized by an increase in the number and size of infiltrates.
- Laboratory research. Microscopy of sputum, bronchial flushing waters and inoculations of pathological material on nutrient media are performed. Microscopically, a wide mycelium of fungi branching at right angles is well determined. Most zygomycetes grow rapidly on conventional fungal nutrient media. The colony grows within a few days. Identification of the pathological agent is carried out.
- Lung biopsies. Under the control of CT, a transthoracic puncture biopsy of the lung is performed, followed by a pathomorphological examination of the obtained material. Histologically, an angioinvasive process with hemorrhages, vascular thrombosis and signs of necrosis of lung tissue is determined.
Currently, specialists in the field of practical pulmonology and infectology are developing rapid serological tests for the diagnosis of zygomycosis. The weak immune response of patients, the small amount of antibodies formed complicate this work. Some laboratories experimentally use ELISA and immunodiffusion for diagnostic purposes.
Pulmonary mucormycosis treatment
Taking into account the speed and severity of the course of the pathological process, treatment should be started immediately and carried out in a hospital. The combination of conservative and surgical measures can significantly reduce mortality. Particular attention is paid to the risk factors for the development of the disease. The correct tactics for the treatment of the pulmonary form of this pathology include:
- Therapy of the underlying disease. If possible, the impact of risk factors on the patient’s body should be minimized. Diabetic sufferers need to normalize blood glucose levels and eliminate ketoacidosis. For patients taking deferoxamine, cytostatics and corticosteroids, these drugs are temporarily excluded from the treatment regimen or prescribed in minimal doses.
- Antifungal therapy. The causative agents of the disease are resistant to many antimycotics. Mucormycosis can develop against the background of preventive antifungal therapy with triazole derivatives. The drugs of choice in the treatment of this pathology are polyenes (amphotericin B and its lipid complex) in high therapeutic doses. Clinical trials of drugs of the echinocandin class are being conducted. The effectiveness of their effect on zygomycetes in monotherapy and in combination with polyenes is evaluated.
- Surgical intervention. Excision of necrotic lung tissue is performed. There is often a need for repeated resections of the lungs until the complete removal of necrosis sites. Surgical treatment is necessarily performed against the background of antifungal therapy. Hyperbaric oxygenation, which increases the killer functions of neutrophils, is used as an auxiliary method.
Prognosis and prevention
Until recently, pulmonary mucormycosis led to the death of patients in 100% of cases. In recent years, with timely treatment, mortality has been reduced by about 2 times. Half of the patients may have a full recovery. The prognosis worsens significantly with the further spread of zygomycetes by lymphogenic and (or) hematogenic pathways and the development of a disseminated form of the disease. Specific prevention of the disease has not been developed. Patients with risk factors need regular medical supervision, treatment of the underlying pathology.
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