Acute hematogenous disseminated pulmonary tuberculosis in children

　　1. Etiology

　　Primary tuberculosis is a disease caused by the first invasion of the tuberculosis bacillus into the body. There are 4 types of tuberculosis bacilli: human, bovine, avian, and murine. The human and bovine tuberculosis bacilli are pathogenic to humans. The majority of pediatric tuberculosis in China is caused by human tuberculosis bacilli. The resistance of the tuberculosis bacillus is strong, in addition to its acid-fast, alkali-fast, alcohol-resistant characteristics, it also has strong resistance to cold, heat, dryness, light, and chemical substances. Wet heat has a strong bactericidal effect on tuberculosis bacilli, and it can be killed at 65℃ for 30 minutes, 70℃ for 10 minutes, and 80℃ for 5 minutes. Dry heat has a poor bactericidal effect, and it takes more than 20 minutes at 100℃ to kill, so dry heat sterilization requires a high temperature and a long time. The tuberculosis bacilli in sputum can be killed within 2 hours under direct sunlight, while ultraviolet light only needs 10 minutes. Conversely, in dark places, it can survive for several months. If the tuberculosis bacilli in sputum are disinfected with 5% carbolic acid (phenol) or 20% bleaching powder solution, it takes 24 hours to take effect.

　　2. Pathogenesis

　　Children have a high level of allergic status, especially a highly allergic state of the vascular system, with increased permeability of the vascular wall. When the body's immune resistance is weakened, it is mainly the caseous lymph nodes in the primary focus or around the tracheobronchial tract that invade the blood vessels, a large number of tuberculosis bacteria enter the blood circulation, and produce bacteremia through the invasion route, quantity, frequency, and interval time, and then invade the pulmonary interstitium and pulmonary parenchyma to form millet nodules. Due to the different invasion routes of the tuberculosis bacteria, the location and type of occurrence are also different. When the tuberculosis bacteria invade the pulmonary artery and bronchial artery through the right heart into the small circulation, it causes millet-type pulmonary tuberculosis. When the tuberculosis bacteria invade the pulmonary veins and enter the systemic circulation through the left heart, it spreads to the whole body organs such as the lungs, brain, liver, spleen, kidneys, intestines, and meninges, pleura, peritoneum, and pericardium, causing systemic millet tuberculosis. In addition, after acute infectious diseases, when the body's immune resistance is reduced or long-term and large amounts of immunosuppressive agents are used, it promotes the deterioration and progression of the tuberculosis focus, promotes the erosion of the lesions into the blood vessels, and increases the opportunity for a large number of tuberculosis bacilli to enter the blood, which can lead to this disease.

　　Acute hematogenous disseminated pulmonary tuberculosis not only invades the lungs but can also cause systemic millet-like changes. The most common complication is tuberculous meningitis, a cerebrovascular disease caused by tuberculosis bacteria. In recent years, there has been a trend of increasing incidence of tuberculous meningitis. If treatment is delayed, it can lead to serious sequelae, even affecting the patient's life. It can also cause millet-like nodular lesions in the liver, spleen, kidneys, bones, and other organs. Symptoms such as meningeal irritation, obvious intoxication, malnutrition, heart failure, purpura, or bleeding may occur.

　　Acute hematogenous disseminated pulmonary tuberculosis is a sepsis caused by tuberculosis bacteria, with an acute onset and often with obvious symptoms of tuberculosis intoxication. It is often characterized by high fever with a remittent or稽留 fever pattern, with some patients experiencing night sweats, weight loss, fatigue, poor appetite, and general malaise. Respiratory symptoms often include cough, sputum, and some patients may have hemoptysis, chest pain, and other symptoms. Gastrointestinal symptoms may include poor appetite, abdominal distension, diarrhea, constipation, and other symptoms. In addition, female patients may experience amenorrhea and other symptoms. The occurrence of tuberculous meningitis may lead to symptoms such as headache, vomiting, and signs of increased intracranial pressure and meningeal irritation. Severe cases may present with drowsiness, coma, and other changes in consciousness. Chronic or subacute hematogenous disseminated pulmonary tuberculosis has a slow onset and a prolonged course. Clinical symptoms may include fever, night sweats, and fatigue, with less severe symptoms of tuberculosis intoxication than acute cases, and respiratory symptoms may be more prominent.

　　One: Control the source of infection and reduce the opportunity of transmission

　　Patients with positive sputum for tuberculosis are the main source of infection for pediatric tuberculosis. Early detection and rational treatment of patients with positive sputum tuberculosis are fundamental measures for preventing pediatric tuberculosis. Family members of infants and young children with active tuberculosis should undergo detailed examinations (such as chest X-rays, PPD, etc.). Staff in primary schools and kindergartens should have regular physical examinations to detect and isolate the source of infection in a timely manner, which can effectively reduce the chance of children being infected with tuberculosis.

　　Two: Popularize the BCG vaccination

　　Practice has proven that vaccination with BCG vaccine is an effective measure for preventing tuberculosis in children. The BCG vaccine was invented by the French physician Calmette and Guerin in 1921, and is also known as B.C.G. In China, the BCG vaccine is administered to newborns, according to regulations, the vaccine is injected intradermally at the upper end of the deltoid muscle of the upper arm, with a dose of 0.05mg per injection. The scratch method is now rarely used. The Ministry of Health notified in 1997 to cancel the BCG revaccination plan for children aged 7 and 12. However, it is still possible to give revaccination to children of that age group if necessary. The BCG vaccine for newborns can be administered on the same day as the hepatitis B vaccine, if the arms are available.

　　Three: Preventive chemotherapy

　　It is mainly used for the following objects:

　　1. Children under 3 years old who have not been vaccinated with BCG and have a positive tuberculin test.

　　2. Those in close contact with patients with open pulmonary tuberculosis (usually family members).

　　3. Children whose tuberculin test recently changed from negative to positive.

　　4. Children with strong positive reactions in the tuberculin test.

　　5. Children with positive tuberculin tests who need to use adrenal cortical hormones or other immunosuppressants for a relatively long time.

　　1. X-ray chest film

　　In the early stage, it presents as a diffused reticular shadow, and after two weeks of onset, fine nodular shadows appear, which are basically uniform in size and shape, widely distributed in both lungs. Most acute hematogenous disseminated pulmonary tuberculosis shows a typical 'three uniform' appearance, that is, millet nodules with uniform size, density, and distribution. Some are accompanied by patchy, strand-like, and/or cavitation shadows.

　　2. Pulmonary CT

　　Acute hematogenous disseminated pulmonary tuberculosis manifests as millet nodules of 1-3mm in diameter, uniform in density and distribution. Subacute and chronic patients mainly show nodules of 3-7mm in size, density, and distribution in the upper middle lung fields. The borders of the nodules are generally clear, but some may show blurred borders; the nodules are randomly distributed in the pulmonary lobules, interlobular septa, and pleura. Some patients may show patchy, fibrous strand-like, and/or cavitation shadows on CT, accompanied by mediastinal and/or hilar lymph node enlargement, and varying degrees of pleural effusion or pleural thickening.

　　3. Sputum smear or culture for Mycobacterium tuberculosis

　　Positive sputum smear or culture for Mycobacterium tuberculosis is the gold standard for diagnosing pulmonary tuberculosis. However, the positive rate of sputum bacteria in hematogenous disseminated pulmonary tuberculosis is only about 30%. Moreover, the positivity of sputum bacteria is affected by many factors, such as improper selection of sputum specimens, insufficient number of sputum examinations, intermittent sputum shedding, and obstruction of the draining bronchus. Fiberoptic bronchoscopy can directly brush or biopsy from around the lesion, thereby improving the microbiological basis for diagnosis.

　　4. Tuberculin Test

　　It is an auxiliary diagnostic method in the comprehensive diagnosis of tuberculosis. For patients under 3 years old with strong positive reactions, they should be considered as having active tuberculosis with recent infection. Negative reactions in the tuberculin test, in addition to indicating the absence of tuberculosis infection, should also consider the following situations: it takes 4-8 weeks after tuberculosis infection to establish a sufficient变态 reaction, and before this变态 reaction occurs, the tuberculin test may show negative results. The tuberculin reaction may also temporarily disappear in patients receiving immunosuppressive drugs such as corticosteroids or those with malnutrition. In severe tuberculosis and various critically ill patients, there may be no reaction to the tuberculin test, or only weakly positive, which is related to the temporary suppression of human immunity and变态 reaction. When the condition improves, the reaction may turn positive. Other conditions such as immune system defects of the lymphocyte immune system (such as sepsis, lymphoma, sarcoidosis, AIDS, etc.) may also show negative reactions in the tuberculin test, especially in the elderly or those with physical decline.

　　5. IFN-γ in vitro release detection

　　After Mycobacterium tuberculosis infects the human body, it can activate the immune system to produce effector T lymphocytes and memory T lymphocytes specific for Mycobacterium tuberculosis. When these specific T lymphocytes encounter the Mycobacterium tuberculosis antigen again, they can be activated and secrete cytokines (such as IFN-γ). Therefore, detecting IFN-γ in the patient's whole blood or body fluid after specific antigen stimulation is helpful for the diagnosis of smear-negative pulmonary tuberculosis.

　　6. Other tests

　　Including blood routine, tuberculosis bacterium TaqMan-PCR, PPD skin test, antituberculosis antibody, erythrocyte sedimentation rate, etc., which have certain reference significance for diagnosis.

　　The appropriate diet for pediatric patients with acute hematogenous disseminated pulmonary tuberculosis mainly includes: 1. Eat food that can increase tissue immunity; 2. Eat high-protein food; 3. Eat food with high amino acid content.

　　I. Treatment

　　1. General treatment

　　Pay attention to strengthen nutrition, reasonably provide vitamins and proteins. For those with poor physical condition and anemia, fresh blood can be infused in small amounts multiple times to enhance the body's resistance.

　　2. Antituberculosis drug chemotherapy

　　Generally, Sm20-30mg/kg (total dose

　　3. Application of adrenal cortical hormones

　　Improve the general condition and alleviate toxic symptoms, promote the absorption of lesions. Prednisone (Prednisone) can be used at a dose of 1-2mg/(kg·d),

　　4. When complicated with meningitis

　　It should be treated according to tuberculous meningitis.

　　5. Severe pulmonary lesions

　　If there is extensive fusion and heart function insufficiency, consider using digitalis preparations or using isoniazid (INH) plus dexamethasone for nebulizer inhalation to improve cardiorespiratory function.

　　II. Prognosis

　　If this disease can be diagnosed early and treated actively with reasonable, effective, and sustained combined therapy, the prognosis is good and cure is expected. If the diagnosis and treatment are delayed and pulmonary tuberculosis is complicated, the prognosis is poor.