Etiology
The main pathogen of the disease is Mycoplasma pneumoniae, which belongs to the class Zoobacteria, genus Mycoplasma, and is the smallest of the pathogenic microorganisms known to live independently between bacteria and viruses and can pass through bacterial filters. The pathogen is 125-150 mm in diameter, similar in size to a mucovirus, has no cell wall, and is naturally resistant to antibacterial drugs that act on the cell wall. Therefore, it is spherical, rod-shaped, filamentous and other forms, Gram stain negative. It is resistant to freezing and can only survive for a few hours at 37°C.
Clinical manifestations
Incubation period 2-3 weeks (8-35 days). Symptoms vary in severity. Most of them are not urgent in onset, with fever, anorexia, cough, chill, headache, sore throat and pain under the sternum, with fever and cough as the main manifestations. The body temperature is 37℃-41℃, most of them are around 39℃, which can be persistent or flaccid, or only low fever, or even no fever. Most of them have a heavy cough, initially dry, followed by sputum (occasionally with a small amount of blood), sometimes with a paroxysmal cough slightly resembling whooping cough. Nausea, vomiting and transient maculopapular rash or urticaria are occasionally seen. There is usually no respiratory distress, but infants may have wheezing and dyspnea. In severe cases, pleural effusion, pulmonary atelectasis, or mediastinal pneumonia, pneumothorax, or necrotizing pneumonia may occur. In a few cases, the disease progresses rapidly and respiratory distress and even death may occur.
Signs vary according to age, but older children often lack significant chest signs. In infancy, there may be mild turbid sounds on percussion, decreased breath sounds, wet rales, and sometimes signs of obstructive emphysema. In children with sickle cell anemia complicated by this pneumonia, the symptoms are often worse, with dyspnea, chest pain and pleural effusion.
The natural course of the disease varies from a few days to 2-4 weeks, with most fevers resolving in 8-12 days and recovery taking 1-2 weeks. complete resolution of the x-ray image extends for 2-3 weeks longer than the symptoms. Occasionally, relapses are seen. About 25% of children have other systemic manifestations, such as skin, mucosal system, cardiovascular system, hematological system, nervous system, and digestive system. The onset of the disease is approximately 2 days to several weeks.
Examination
1.Imaging examination
X-rays show mostly unilateral lesions, mostly in the lower lobe, sometimes only with increased shadowing in the hilum, mostly with uneven cloudy pulmonary infiltrates, extending outward from the hilum to the lung fields, especially in the lower lobe of both lungs, with a few large lobar solid shadows. Pulmonary atelectasis may be seen. The infiltrates often dissipate in one area while new infiltrates occur elsewhere. Sometimes there is a bilateral diffuse reticular or nodular infiltrative shadow or interstitial pneumonia without solid lung segments or lobar changes. Mild signs and significant chest radiograph shadows are one of the features of the disease.
CT examination of the chest can provide more diagnostic information than ordinary chest X-ray and help to differentiate it from other lung diseases such as tuberculosis, but the indications for CT examination should be strictly controlled.
2.Ethiological examination
(1) Isolation and culture of Mycoplasma pneumoniae from the child’s throat, nasal cavity, pleural fluid or body fluid is a reliable criterion for the diagnosis of infection, but routine culture takes 10-14 days or even longer, and is of little value for early diagnosis.
(2) Specific serological tests include: gelatin particle agglutination test (PA) and enzyme-linked immunosorbent assay (ELASA), both of which can confirm the diagnosis of Mycoplasma pneumoniae infection when the antibody titer is ≥4-fold higher or lower in the recovery and acute phases; non-specific tests include: condensation set test (CA), which has a positive rate of only 50% at the time of infection, and some viral infections can induce the production of serum cold agglutinin, which is only of It is only of reference value.
Diagnosis
The main diagnostic points are.
1. persistent and severe cough, with x-ray findings being far more significant than physical signs. If several cases occur simultaneously in older children, an epidemic case is suspected and the diagnosis can be confirmed early.
2. The white blood cell count is mostly normal or slightly elevated, the blood sedimentation is more rapid, and the Coombs test is positive.
3. Penicillin, streptomycin and sulfonamides are ineffective against the disease.
4.Serum agglutinin (IgM type) titers mostly rise to 1:32 or higher, the more severe the disease, the higher the positive rate. Cold agglutinins mostly appear at the end of the first week after the onset of the disease, reaching a peak in the 3rd-4th weeks, and then gradually decrease and disappear in 2-4 months.
5.Serum specific antibody determination has diagnostic value and is often used clinically by complement binding test, indirect hemagglutination test, indirect immunofluorescence method and enzyme-linked immunosorbent assay. In addition, enzyme-linked adsorbent assay can be used to detect antigen. In recent years, domestic and foreign applications of DNA probes and PCR detection of Mycoplasma pneumoniae DNA diagnosis has the advantages of rapid and high specificity.
6, with the patient’s sputum or pharyngeal wash culture mycoplasma takes too long, often 2-3 weeks, so it is not very helpful to clinical.
Differential diagnosis
It needs to be differentiated from bacterial pneumonia, tuberculosis, bronchial foreign body, Chlamydia pneumonia, and viral pneumonia.
Treatment
The treatment of pediatric MP pneumonia is based on the same principles as that of general pneumonia, with a combination of therapeutic measures. Including general treatment, symptomatic treatment, the application of antibiotics, adrenal corticosteroids, and the treatment of extra-pulmonary complications and other five aspects.
1.General treatment
(1) respiratory isolation because mycoplasma infection can cause a small epidemic, and the time to discharge mycoplasma after the disease in children is long, up to 1-2 months beyond. For children or children with a history of close contact, respiratory isolation should be done as much as possible to prevent reinfection and cross-infection.
(2) Care to keep the room air fresh, supply easily digestible, nutritious food and sufficient fluids. Keep the oral hygiene and respiratory tract unobstructed, turn the child frequently, pat the back and change the position to promote the discharge of secretions, and if necessary, aspirate appropriately to remove mucous secretions.
(3) Oxygen therapy should be given in time to those who have serious condition with hypoxia or serious airway obstruction.
2.Symptomatic treatment
(1) The purpose of expectoration is to make the sputum thin and easy to discharge, otherwise it is easy to increase the chance of bacterial infection. In addition to strengthening turning, back patting, nebulization and sputum aspiration, expectorant can be used.
(2) To calm asthma, bronchodilators such as aminophylline can be used for severe asthma, and albuterol can also be used for inhalation.
3.Application of antibiotics
The antibiotics that can inhibit protein synthesis should be used, including macrolides, tetracyclines, chloramphenicol, etc. Macrolides are the antibacterial drugs of choice for mycoplasma pneumonia, and azithromycin is the first choice for treatment. In addition, there are also lincomycin, chloramphenicol, vancomycin and sulfonamides available.
4, the application of adrenal glucocorticoids
For the acute stage of rapid development of severe MP pneumonia or pulmonary lesions that extend and appear pulmonary atelectasis, interstitial fibrosis, bronchiectasis or extra-pulmonary complications, adrenal corticosteroids can be applied. For example, hydrocortisone or hydrocortisone succinate, dexamethasone, prednisone, etc. Pay attention to exclude tuberculosis and other infections when applying hormones.
5.Extrapulmonary complications
Give the appropriate symptomatic treatment.