Pulmonary cryptococcosis is a subacute or chronic visceral mycosis caused by Cryptococcus neoformans, which mainly invades the lungs and central nervous system, but can also invade bones, skin, mucous membranes, and other organs. This fungus only causes mild inflammatory reaction after infection, and the disease occurs mostly in immunosuppressed hosts, such as AIDS patients, and approximately 20% occur in immunocompetent healthy persons.
Etiology
The pathogenic cryptococci are mainly Cryptococcus neoformans and Cryptococcus gattii. The cells are mostly round or oval, do not form hyphae and spores, and reproduce by budding. Cryptococcus neoformans is a saprophytic, parasitic yeast that can grow at 37°C and has a capsule. According to capsule antigen, Cryptococcus is divided into 4 serotypes: A, B, C, and D. Infections caused by different variants and different serotypes show certain regional differences. Type A, D, and AD are distributed globally and widely found in soil and pigeon feces, and are associated with infection in immunosuppressed patients, particularly AIDS patients; while Cryptococcus gattii, mostly type B and C, is found in tropical and subtropical regions. The fungus can be isolated from soil, pigeon feces, and fruits, and can also be isolated from the skin, mucous membranes, and feces of healthy persons. Pathogens in the environment mainly enter the human body through the respiratory tract, but also through the skin or digestive tract, causing disease or turning the hosts into carriers. The incidence of Cryptococcus neoformans infection in HIV patients is nearly 10%, ranking fourth in infectious complications. Cryptococcosis can occur at any age, mainly in children and adults over age 40. Cryptococcus neoformans does not produce toxins, and infection does not cause tissue destruction, hemorrhage, infarction, and necrosis, nor does it cause fibrosis and calcification. The direct effect of pathogens on tissues is increased occupied space and compression
Clinical manifestations
Clinical manifestations include insidious onset, fever, cough, little white expectoration, tachypnea, thoracodynia, hemoptysis, emaciation, and diaphoresis, and there may be no symptoms. Small localized patchy opacities in the lungs are common on the chest x-ray, and the disease is often misdiagnosed as tuberculosis or pneumonia caused by atypical pathogens. The lung lesions can subside spontaneously without antifungal treatment, but may develop slowly in some patients, forming dissemination. In patients with slow development, chronic inflammation and granulomas can gradually form, and chest x-ray shows nodular or massive opacities, which are easily misdiagnosed as lung cancer. Dissemination may cause extrapulmonary infection, and meningoencephalitis or other extrapulmonary infections may occur in few patients when the lesions are subsiding or after the lesions have subsided. In immunosuppressed patients, chest x-ray shows multiple solid patches, diffuse interstitial infiltrations, or nodules in both lungs, and the involvement of the pleura can cause exudation and pneumothorax, accompanied by hilar lymphadenopathy.
Diagnosis
The growth of Cryptococcus in sputum culture is very helpful for the diagnosis of pulmonary cryptococcosis, but it is not sufficient for a definite diagnosis, because it can colonize the respiratory tract and does not necessarily cause the disease. A definite diagnosis requires direct sampling and culture from the lower respiratory tract or lung tissue. Cerebrospinal fluid in India ink staining can be examined in microscopy, and If a round, thick-walled body with a translucent outer ring is seen, Cryptococcus neoformans can be confirmed. In tissues in Grocott-Gomori methenamine silver (GMS) staining or Fontana-Masson staining (FMS), Cryptococcus can be found. Latex agglutination test for detection of cryptococcal antigen has a high diagnostic value for cryptococcal infection.
Treatment
Fluconazole, itraconazole, and amphotericin B can be used for treatment. In immunocompetent patients, if asymptomatic, the treatment plan is oral fluconazole 200 - 400 mg/d for 3 - 6 months; and if symptomatic, the course is 6 - 12 months. In severe patients, particularly with cryptococcal meningitis, a combination of two antifungal drugs, such as amphotericin B in combination with flucytosine, can be given. For pulmonary cryptococcosis that is surgically resected without preoperative chemotherapy, oral fluconazole 200 - 400 mg/d for 2 - 4 months after surgery is recommended.