Pulmonary fungal infections are bronchio-pulmonary diseases caused by fungal infections, including primary and secondary pulmonary fungal infections. Fungal spores, etc., are inhaled into the human lungs and cause disease called primary pulmonary fungal infections. Fungal infections in other parts of the body that cause disease through lymph or blood to the lungs are called secondary pulmonary fungal infections. The clinical manifestations of pulmonary fungal infections are not specific, and the diagnosis is based on the diagnostic criteria of invasive pulmonary fungal disease classification (grade 3), which is divided into confirmatory, clinical diagnosis, and proposed diagnosis. A definite diagnosis requires only microbiological evidence (smear and culture) determined by histology or sterile body fluid testing, and does not involve host factors. Clinical diagnosis requires a combination of host factors, clinical features, and microbiologic evidence. The proposed diagnosis is consistent with host factors, clinical features, and lack of microbiological evidence. Immunological tests for positive cell wall component (1,3)-β-D-glucan antigen test (G test) and galactomannan antigen test (GM test) in serum have important diagnostic aids. Several common diagnoses of pulmonary fungal infections are described below: 1. Pulmonary candidiasis is seen in high-risk groups such as granulocyte deficiency, indwelling central venous catheters, major abdominal surgery, hormone and antibiotic therapy, diabetes, renal insufficiency, and organ transplantation. Clinical symptoms include unexplained persistent fever, respiratory symptoms, but mild signs. Cough, even severe, with small amounts of white mucus sputum or thick sputum. The hematogenous disseminated form often presents with rapidly progressive circulatory and respiratory failure. x-ray shows bronchopneumonia changes or lamellar infiltrates or fusion, and cavity formation may be present. The diagnosis is confirmed by direct smear or culture of lower respiratory secretions, lung tissue, pleural fluid, and blood for Candida. Sputum direct smear or culture of Candida is not diagnostic of fungal disease, because 10%-20% of normal people can find Candida albicans in sputum, if 3% hydrogen peroxide containing gargle 3 times from deep cough sputum (qualified sputum) ≥ 2 times in a row to culture the same species of Candida is diagnostic reference value. Positive blood culture of Candida is a reliable diagnostic evidence of Candida bacteremia. Some patients with positive G test (need to exclude false positive), can provide important reference for clinical diagnosis. 2, pulmonary aspergillosis Clinical manifestations are complex, with 3 common types: allergic bronchopulmonary aspergillosis (mostly allergic), Aspergillus (the most common symptom is hemoptysis) and invasive pulmonary aspergillosis (for granulocyte deficiency or unexplained fever, dry cough, chest pain, hemoptysis during treatment with broad-spectrum antibiotics, hormones, immunosuppressants, etc.). Diagnostic criteria for allergic bronchopulmonary aspergillosis include: (1) recurrent asthma-like attacks; (2) increased peripheral blood eosinophils ≥ 1X109/L; (3) transient or wandering pulmonary infiltrates on X-ray; (4) total serum IgE concentration ≥ 1000 mg/ml; (5) positive skin test for Aspergillus antigen; (6) positive serum precipitin antibodies; (7) specific anti- Aspergillus IgE and IgG (8) central cystic bronchiectasis. The clinical diagnosis of pulmonary aspergillosis can be made on the basis of imaging features, but it needs to be differentiated from other fungal spheres, misfunctions, lung cancer, echinococcal cysts, and lung abscess. Definitive diagnosis requires pathogenesis and histopathology. Pulmonary aspergillosis CT features as a round dense shadow in the lung cavity or pleural cavity with translucent halo shadow at its edge. If the cavity is large, spherical shadows can be seen with the wall of the cavity connected, shaped like a pendulum, spherical shadows can change shape with the change of body position. If the cavity is small and the spherical lesion fills most of the cavity, the halo shadow is small and only a narrow half-moon shaped translucent band. CT features of invasive pulmonary aspergillosis: early inflammatory shadow with a thin foggy exudate around it (“halo sign”), followed by an inflammatory lesion with a solid air cavity and visible bronchial inflation sign, and then a lesion with a translucent half-moon area (“air half-moon sign”) and further may become complete necrotic cavities. The diagnosis is based on the 3 levels of diagnostic criteria mentioned above, and a positive GM test provides an important reference. 3, pulmonary cryptococcosis Cryptococcus neoformans and its variants (at least 9 species) are the main pathogenic cryptococci. Clinical symptoms and signs: from asymptomatic to acute pneumonia manifestations, varies greatly and is not specific, combined with meningitis may have headache, dizziness, vomiting and other signs of meningeal irritation. 4, Pneumocystis pneumonia The vast majority of this disease is seen in patients with AIDS and other causes of cellular immunosuppression. Fever, dry cough and progressive dyspnea, and hypoxemia are the main clinical symptoms of the disease. Signs are rare even though large inflammatory changes are present in the lungs. Imaging shows early diffuse alveolar and interstitial infiltrative shadows that rapidly fuse and become extensive pulmonary solids with visible bronchial inflation signs. There is usually no involvement of the pulmonary apices, lung bases or outer lung bands. The diagnosis should be considered if the patient has persistent fever >96 hours and has failed to respond to aggressive antibiotic therapy; has signs and symptoms of pulmonary infection: cough, sputum, hemoptysis, chest pain and dyspnea and pulmonary rales or pleural friction sounds; and new non-specific pulmonary infiltrative shadows are seen on imaging in addition to the main clinical features. Coughing, sputum conduction, bronchoalveolar lavage specimens or lung biopsy specimens are still the basic diagnostic methods for this disease.