Pediatric mycoplasma pneumonia

　　1, Etiology

　　The main pathogen of this disease is Mycoplasma pneumoniae (Mycoplasma pneumoniae), an intermediate microorganism between bacteria and viruses, known as 'pleuropneumonia-like microorganism'. It is the smallest among the known independent living pathogens, can pass through bacterial filters, requires a special medium containing cholesterol, and colonies appear only after 10 days of inoculation, which are very small and rarely exceed 0.5mm. The diameter of the pathogen is 125-150nm, similar in size to mucous viruses, has no cell wall, and therefore presents in various shapes such as spherical, rod-shaped, and filamentous, and is Gram-negative. It can withstand freezing. It can only survive for a few hours at 37℃.

　　2, Pathogenesis

　　Mycoplasma pneumoniae is transmitted through droplets, invades the respiratory mucosa, and adheres to the receptors on the cell membrane of susceptible hosts through its special structure, proliferates and releases toxic substances such as hydrogen peroxide, enzymes, and membrane lipids, causing tissue damage. Its basic pathological change is interstitial pneumonia and acute bronchiolitis. Under the microscope, local mucosal tissue shows congestion, edema, and thickening, cell membranes are damaged, cilia movement of epithelial cells disappears, monocytes and plasma cells infiltrate, and neutrophils and necrotic epithelial cells can be seen in the bronchioles.

　　1, 7% have neurological complications

　　Asymptomatic meningitis, meningoencephalitis, cranial nerve palsy, cerebellar ataxia, peripheral neuritis, and other conditions. Most cases present with respiratory symptoms first, followed by neurological symptoms 7 to 14 days later, and approximately 1/5 of patients present with neurological symptoms directly.

　　2. 4.5% have cardiovascular system complications

　　Complications may include myocarditis, pericarditis, acute heart failure, and atrioventricular block. Among these complications, about 70% of children show transient or mild symptoms, or only changes in electrocardiogram, with a few children developing severe cardiovascular damage.

　　3. 12% to 44% have gastrointestinal symptoms

　　Mostly non-specific manifestations, such as anorexia, nausea, vomiting, abdominal pain, diarrhea, constipation, and other symptoms, often occur in the early stage of the disease. In addition, hepatitis, liver enlargement, and elevated serum transaminases may occur, but the liver function of most patients tends to return to normal as the pulmonary inflammation resolves.

　　4. 25% have skin damage

　　Complications include various types of rashes, such as macules, maculopapular eruptions, vesicles, urticaria, and purpura, which often occur during the fever phase. Males are more prone to this.

　　5. 15% to 45% have muscle and joint damage

　　Joint pain and non-specific muscle pain may occur. In arthritis and joint pain, the main symptoms are polyarticular involvement of large and medium-sized joints such as the knee, ankle, and shoulder joints, which are often migratory. Changes in muscles, such as transient muscle soreness, may also occur.

　　1. Incubation period

　　About 2 to 3 weeks (8 to 35 days).

　　2. Symptoms

　　The symptoms vary in severity, with most onset not being very acute, including fever, anorexia, cough, aversion to cold, headache, sore throat, pain beneath the sternum, and other symptoms. The body temperature ranges from 37℃ to 41℃, most commonly around 39℃, and can be persistent or remittent, or even just low-grade fever, with or without fever. Most patients have severe cough, starting with dry cough and followed by expectoration of sputum (occasionally containing a small amount of blood), and sometimes paroxysmal cough that slightly resembles whooping cough. Nausea, vomiting, and transient maculopapular eruptions or urticaria may occur occasionally. Generally, there is no respiratory distress, but infants may have wheezing and respiratory distress. Physical signs vary with age, with older children often lacking significant chest signs, while infants may exhibit mild dullness on percussion, weakened breath sounds, and moist rales. Occasionally, obstructive pulmonary emphysema signs may be present. In children with sickle cell anemia who develop this type of pneumonia, symptoms often worsen, with signs of respiratory distress, chest pain, and pleural effusion. Atypical pneumonia may occasionally be complicated by exudative pleurisy and lung abscess. There is a certain relationship between chronic lung diseases and mycoplasma pneumonia. Berkwick (1970) reported that in 27 asthmatic children, the recurrence increased fourfold. Mycoplasma pneumonia can be accompanied by multiple systemic and organ damage, with extrathoracic lesions involving the skin and mucous membranes, presenting as measles-like or scarlet fever-like rashes, Stevens-Johnson syndrome, etc.; occasionally, non-specific muscle pain and migratory joint pain may occur; the gastrointestinal system may show vomiting, diarrhea, and liver function damage; in the hematological system, hemolytic anemia is relatively common, and we have seen two cases where hemolytic anemia was the initial and main symptom; multiple neuritis, meningomyelitis, and cerebellar injury, etc.; cardiovascular system lesions may occasionally include myocarditis and pericarditis, and bacterial mixed sensation is also rare, with varying levels of white blood cells, most of which are normal, with some slightly elevated, and the erythrocyte sedimentation rate shows moderate acceleration.

　　3. X-ray examination

　　It is mostly unilateral, accounting for more than 80%, most of which are in the lower lobe. Sometimes it is only an increase in pulmonary hilum shadow. Most are irregular cloud-like pulmonary infiltration, extending from the hilum to the lung field, especially common in the lower lobes of both lungs. A few are lobar consolidation shadows, and pulmonary atrophy can be seen. Often, one area subsides while a new infiltration occurs elsewhere. Sometimes it presents as bilateral diffuse reticular or nodular infiltration shadows or interstitial pneumonia, without pulmonary segment or lobe consolidation. The signs are mild but the chest X-ray shadows are significant, which is one of the characteristics of the disease.

　　4. Course of the disease

　　The natural course varies from several to 2-4 weeks, most of which subside within 8-12 days, and the recovery period requires 1-2 weeks. X-ray shadows completely disappear, lasting longer than symptoms by 2-3 weeks, and occasionally recurrence may be seen.

　　Attention should be paid to rest, care, and diet. If necessary, small amounts of antipyretic drugs and traditional Chinese medicine can be taken. Other symptomatic therapies are the same as those described for bronchitis. Mycoplasma is sensitive to tetracyclines and macrolides, and erythromycin is the first choice of drug, with a dose of 30mg/(kg·d), taken orally three times a day. It can improve clinical symptoms, reduce pulmonary shadows, and can shorten the course of the disease. The course of erythromycin is 2-3 weeks. In addition, drugs such as mefloquine, rifampin, and acetylspiramycin also have therapeutic effects. In severe cases, adrenal cortical hormones can be added. The prognosis is good, although the course of the disease may be long at times, but it can be completely recovered. Complications are rare, and only otitis media, pleural effusion, hemolytic anemia, myocarditis, pericarditis, meningitis, and skin and mucosal syndrome are occasionally seen. However, recurrence can occur occasionally, and sometimes pulmonary lesions and lung function recovery are slower.

　　1. Peripheral blood

　　The white blood cell count is mostly normal, but there may be an increase or a decrease in white blood cells.

　　2. Blood biochemistry

　　Erythrocyte sedimentation rate is usually increased, mostly mild to moderate, and the titer of anti-O antibody is normal. Part of the children's serum transaminase, lactic dehydrogenase, and alkaline phosphatase levels are elevated.

　　3. MP detection

　　Early children can be tested for PCR in the sputum and other secretions of children and in the lung tissue for MP-16SRDNA or P1 adhesion protein gene, and MP can also be isolated and cultured from sputum, nasal secretions, and throat swabs.

　　4. Serum antibody detection

　　Serum antibodies can be measured by complement fixation test, indirect hemagglutination test, enzyme-linked immunosorbent assay, indirect immunofluorescence test, or early diagnosis can be obtained by detecting antigens.

　　5. Sputum, nasal, and throat swab cultures

　　Pneumonia mycoplasma can be obtained, but it takes about 3 weeks, and antiserum can be used to inhibit its growth. Red blood cell lysis can also be used to confirm negative culture. About half of the cases produce antibodies two weeks after the onset.

　　6. Red blood cell cold agglutination test

　　Positive, the titer is above 1:32, and the titer increases 4 times during the convalescent period, which is significant for about 40-50% of cases with streptococcal MG agglutination test positivity, and the titer of MG streptococcal agglutinin in the blood is 1:40 or higher. The titer gradually increases to 4 times, which is more significant.

　　1. Use 50 grams of lily and 200 grams of Job's tears. Add 5 bowls of water, boil to 3 bowls, and take in three divided doses, one dose per day.

　　2. Take 30 grams of walnuts, 30 grams of rock sugar, and 150 grams of pears. Grind together and cook with water for consumption. Take 1 spoonful, three times a day.

　　3. Take 10 grams of codonopsis, 15 grams of jujube (with the seeds removed), and 150 grams of glutinous rice. Add an appropriate amount of water to cook into porridge, and season with sugar before serving.

　　4. Use 10 grams of bitter almond (peel and crush the tips), 1-2 duck pears, and an appropriate amount of rock sugar. First, cut the duck pear into pieces and remove the core, then cook with the almond. When the pear is cooked, add rock sugar and drink as tea.

　　First, treatment

　　The treatment of pediatric mycoplasma pneumonia is basically the same as that for general pneumonia, taking comprehensive treatment measures including general treatment, symptomatic treatment, the use of antibiotics, adrenal cortical hormones, and the treatment of extrapulmonary complications, covering 5 aspects.

　　1. General treatment

　　(1) Respiratory isolation: Due to the potential for a small outbreak caused by mycoplasma infection, and the time it takes for children to excrete mycoplasma after illness, which can last up to 1-2 months, symptoms in infancy are only upper respiratory tract infection. Pneumonia occurs after repeated infections. In addition, it is easy to be re-infected with other viruses during the MP infection period, leading to severe and protracted illness. Therefore, respiratory isolation should be done as much as possible for children with close contact history or for children with mycoplasma pneumonia, to prevent re-infection and cross-infection.

　　(2) Nursing care: Attention should be paid to rest, care, and diet. Small doses of antipyretic drugs can be taken if necessary, as well as traditional Chinese medicine (see bronchitis). Keep the indoor air fresh, maintain a room temperature of 18-20°C, and a relative humidity of 60% is preferable. Provide easily digestible, nutritious food and sufficient fluids. Maintain oral hygiene and keep the respiratory tract unobstructed. Frequently turn the child over, pat the back, change positions, promote the excretion of sputum, and if necessary, suction sputum to remove thick secretions.

　　(3) Oxygen therapy: Oxygen should be administered promptly to patients with severe illness and signs of hypoxia, or those with severe airway obstruction. The method is the same as that for general pneumonia.

　　2. Symptomatic treatment

　　Other symptomatic therapies are the same as those described for bronchitis.

　　(1) expectoration: The purpose is to make the sputum thin and easy to expel. Otherwise, it is easy to increase the chance of bacterial infection. However, there are few effective expectorants. In addition to strengthening turning over, patting the back, nebulization, and suction, expectorants such as bromhexine (Bisolvon), acetylcysteine (Mucifresh) can be used. Since cough is the most prominent clinical manifestation of mycoplasma pneumonia, frequent and severe coughing will affect the sleep and rest of the child, and appropriate sedatives such as chloral hydrate or phenobarbital can be given. Small doses of codeine can be given for cough suppression, but the frequency should not be too high.

　　(2) Asthma relief: For patients with severe asthma, bronchodilators such as aminophylline can be used orally at a dose of 4-6mg/(kg·d) every 6 hours; or salbutamol (albuterol) can be inhaled, etc.

　　3. The application of antibiotics

　　According to the microbiological characteristics of MP, antibiotics that can hinder the synthesis of the cell wall of microorganisms such as penicillin are ineffective against mycoplasma. Therefore, when treating MP infection, antibiotics that can inhibit protein synthesis should be selected, including macrolides, tetracyclines, chloramphenicol, and others. In addition, there are also lincomycin, clindamycin (chloro-lincomycin), vancomycin, and sulfonamides such as sulfamethoxazole (SMZ) that can be selected. Mycoplasma is most sensitive to macrolide antibiotics, and erythromycin is the first choice drug.

　　(1) Macrolide antibiotics: Among the above-mentioned antibiotics, macrolide antibiotics such as erythromycin, spiramycin, medemycin, gital霉素 (white mycin) are often used. Among them, erythromycin is the first choice, which is widely used and has a definite therapeutic effect. It has a significant effect on eliminating the symptoms and signs of mycoplasma pneumonia, but it is not ideal for eliminating MP and cannot eliminate the residence of mycoplasma pneumonia. The commonly used dose is 50mg/(kg·d), and the mild cases can be treated with oral administration in 3 doses, and the severe cases can consider intravenous administration. The general duration of treatment is recommended to be not less than 2-3 weeks, and it is easy to relapse if the medication is stopped too early. Commonly used oral preparations include erythromycin estolate (tasteless erythromycin) and erythromycin enteric-coated tablets. It can improve clinical symptoms, reduce lung shadows, and can shorten the course of the disease.

　　Considering that erythromycin has a strong irritation to the gastrointestinal tract and can cause increased blood bilirubin and transaminases, and there are reports of the emergence of resistant strains, people have begun to choose new macrolide antibiotics such as roxithromycin, clarithromycin (amoxicillin), azithromycin, etc., which are easy to tolerate orally, have strong tissue penetration, can penetrate into cells, and have a long half-life. In recent years, gital霉素 (white mycin) has been used effectively in Japan for the treatment of this disease, and the drug has no obvious toxic and side effects, is relatively safe, and the oral dose is 20-40mg/(kg·d), taken in 4 doses, and the intravenous dose is 10-20mg/(kg·d). In addition, acetylmedemycin (meiyoukaimycin), rifampicin, and acetylspiramycin also have therapeutic effects.

　　(2) Tetracycline antibiotics: Although there is a definite therapeutic effect on MP infection, it has many toxic and side effects. Especially the effect of tetracycline on bone and tooth growth, even if it is used for a short period of time, the pigment of tetracycline can combine with calcium in newly formed bones and teeth, causing deciduous teeth to turn yellow. Therefore, it is not suitable to use it before the age of 7 in the period of childhood.

　　(3) Chloramphenicol and Sulfonamides: Because the course of treatment for MP infection is long, and chloramphenicol and sulfonamides have many toxic and side effects, they are not suitable for long-term use, so they are rarely used in clinical practice for the treatment of MP infection.

　　(4) Fluoroquinolones: In recent years, there have been reports of the use of fluoroquinolones for the treatment of MP infection. Fluoroquinolones belong to synthetic antibacterial drugs, which exert antibacterial effects by inhibiting DNA gyrase and blocking DNA replication. Ciprofloxacin (ciprofloxacin), ofloxacin, and other drugs have high concentrations in pulmonary and bronchial secretions, can penetrate the cell wall, and have a half-life of 6.7-7.4h. With a broad spectrum of antimicrobial activity, they have a good therapeutic effect on MP. The former is 10-15mg/(kg·d), taken orally in 2-3 divided doses, or can be administered intravenously in divided doses; the latter is 10-15mg/(kg·d), taken orally in 2-3 divided doses, and the course of treatment is 2-3 weeks.

　　4. Application of Adrenal Glycorticosteroids

　　Adrenal cortical hormones can be added in severe cases. Because it is currently believed that MP pneumonia is an immune response of the human immune system to MP, so for acute MP pneumonia or pulmonary lesions with rapid and severe disease progression, atelectasis, pulmonary interstitial fibrosis, bronchial dilation, or extra-pulmonary complications, adrenal cortical hormones can be applied. Such as hydrocortisone or hydrocortisone succinate, 5-10mg/kg intravenously each time; or dexamethasone 0.1-0.25mg/(kg·d) intravenously; or prednisone (prednisone) 1-2mg/(kg·d), taken orally in divided doses, usually for 3-5 days. When using hormones, pay attention to exclude infections such as tuberculosis.

　　5. Treatment of Extra-pulmonary Complications

　　Currently, it is believed that the occurrence of complications is related to the immune mechanism. Therefore, in addition to actively treating pneumonia and controlling MP infection, hormones can be used according to the condition, and different symptomatic treatment methods can be adopted for different complications.

　　II. Prognosis

　　The prognosis is good, although the course of the disease is sometimes long, it can be completely recovered in the end. Complications are rare, and otitis media, pleural effusion, hemolytic anemia, myocarditis, pericarditis, meningitis, and skin and mucosal syndrome are occasionally seen. However, recurrence is possible, and sometimes pulmonary lesions and lung function recovery are slower.