Mycoplasma pneumonia in children

Introduction to pediatric mycoplasmal pneumonia Mycoplasmal pneumonia (mycoplasmal pneumonia) formerly known as primary atypical pneumonia, condensation-positive pneumonia, is caused by mycoplasma (MP) infection, basic course of interstitial pneumonia and bronchiolitis-like changes, clinical manifestations of intractable severe cough Inflammation of the lungs, MP is one of the important pathogens of childhood pneumonia and other respiratory infections. basic knowledge The proportion of illness: 9.8% Susceptible people: young children Mode of infection: respiratory transmission Complications: myocarditis, acute heart failure

Causes of mycoplasmal pneumonia in children

(1) Causes of the disease

The main pathogen of this disease is Mycoplasma pneumoniae, a kind of "pleural pneumonia-like microorganism" between bacteria and virus. It is the smallest of the pathogenic microorganisms known to live independently. It can pass the bacteria filter and needs cholesterol. The special medium, colonies appear 10 days after inoculation, the colonies are very small, rarely more than 0.5mm, the pathogen diameter is 125 ~ 150nm, similar to the size of mucus virus, no cell wall, so it is spherical, rod-shaped, silky, etc. A variety of forms, Gram-negative, can withstand freezing, can only survive for a few hours at 37 °C.

(two) pathogenesis

Mycoplasma pneumoniae spreads through droplets and invades the mucosa of the respiratory tract. Through its special structure, it is closely adsorbed to the receptor of the cell membrane of the susceptible host, and it proliferates and releases toxic substances such as hydrogen peroxide, enzymes and membrane lipids. Etc, causing tissue damage, the basic pathological changes are interstitial pneumonia and acute bronchiolitis, microscopic local mucosal tissue congestion, edema, thickening, cell membrane damage, epithelial cell cilia movement disappear, monocytes and plasma cells Infiltration, neutrophils and necrotic epithelial cells are seen in the bronchioles.

Prevention of mycoplasmal pneumonia in children

In recent years, many studies on the Mycoplasma pneumoniae vaccine have been carried out abroad, and inactivated vaccines and live attenuated vaccines have been prepared. Wenzel (1977) observed formalin-inactivated Mycoplasma pneumoniae vaccine, which has certain effects.

Should pay attention to rest, care and diet, if necessary, can take a small amount of antipyretics, and take Chinese medicine, other symptomatic treatment is also the same as described in the bronchitis section, mycoplasma is sensitive to tetracycline and macrolide antibiotics, erythromycin is The drug of choice, the dose of 30mg / (kg · d), oral three times a day, can improve clinical symptoms, reduce lung shadows, and shorten the course of the disease, erythromycin treatment for 2 to 3 weeks, in addition to the United States carbamicin, rifamp Pinghe acetylspiramycin is also effective. Adrenal cortical hormone can be added to severely ill children. The prognosis is good. Although the course of disease is sometimes longer, it can be completely recovered. There are few complications. Occasionally, otitis media, thoracic exudate, Hemolytic anemia, myocarditis, pericarditis, meningoencephalitis and skin and mucous membrane syndrome, but occasionally recurrence, sometimes lung lesions and lung function recovery is slower.

Complications of mycoplasmal pneumonia in children Complications Myocarditis Acute heart failure

(1) 7% have neurological complications: such as aseptic meningitis, meningoencephalitis, cranial nerve palsy, cerebellar ataxia, peripheral neuritis, etc. Most cases have respiratory symptoms first, and nerves appear after 7 to 14 days. Systemic symptoms, about 1 in 5 patients, directly with neurological symptoms.

(2) 4.5% have cardiovascular complications: such as myocarditis, pericarditis, acute heart failure, atrioventricular block, about 70% of the above complications are transient or mild symptoms, or only electrocardiogram Changes, a small number of children can develop severe cardiovascular damage.

(3) 12% to 44% have digestive symptoms: Most of them are non-specific, such as loss of appetite, nausea, vomiting, abdominal pain, diarrhea, constipation, etc., often occur in the early stages of the disease, in addition to hepatitis, hepatomegaly, serum Transaminase is elevated, but liver function in most patients tends to normal as the inflammation of the lungs heals.

(4) 25% have skin damage: complicated by rash, rash, various forms, erythema, maculopapular rash, herpes, urticaria and purpura, etc., mostly occur in the fever period, more men.

(5) 15% to 45% have muscle, joint damage: joint pain and non-specific muscle pain can occur, in arthritis and joint pain, mainly how much, middle joints such as knee joint, ankle joint, shoulder joint multi-joint Symptoms, mostly migratory, muscle changes such as transient muscle soreness.

(6) 30% complicated with earache.

Symptoms of mycoplasmal pneumonia in children Common symptoms Nausea soreness Low heat breath sounds weakened dry cough chills Chest pain Pericarditis Anorexia pleural effusion

1. Incubation period

About 2 to 3 weeks (8 to 35 days).

2, symptoms vary in severity, most of the onset is not very urgent, fever, anorexia, cough, chills, headache, sore throat, substernal pain and other symptoms, body temperature at 37 ~ 41 ° C, most at around 39 ° C, can For persistence or relaxation, or only low fever, or even no fever, most coughs are heavy, early dry cough, and then secrete sputum (even with a small amount of bloodshot), sometimes coughing like pertussis, occasionally nausea, vomiting and short-lived The maculopapular rash or urticaria is generally free of dyspnea, but infants may have wheezing and difficulty breathing. The signs vary according to age. Older children often lack significant chest signs. Infancy can be mildly dull in infancy. Breathing The sound is weakened, there is wet rales, sometimes it can be signs of obstructive emphysema. In children with sickle cell anemia, the symptoms are often aggravated. It can be seen that breathing difficulties, chest pain and pleural effusion, mycoplasma pneumonia can be combined. Exudative pleurisy and lung abscess, chronic lung disease and Mycoplasma pneumoniae have a relationship, Berkwick (1970) reported that 27 children with asthma have a 4-fold increase in relapse, mycoplasma pneumonia can be associated with multiple systems, more Official damage, extra-respiratory lesions may involve skin and mucous membranes, manifested as measles-like or scarlet fever-like rash, StevensJohnson syndrome, etc.; occasionally non-specific myalgia and migratory joint pain; vomiting, diarrhea and liver function damage in the gastrointestinal system The blood system is more common in hemolytic anemia. We have seen 2 cases with hemolytic anemia as the first and main symptoms; multiple radiculitis, meningoencephalitis and cerebellar injury; cardiovascular system lesions occasionally myocarditis and pericarditis Bacterial mixed sensation is also rare. White blood cells vary in height, mostly normal, sometimes high, and erythrocyte sedimentation rate shows moderate increase.

3, X-ray inspection

More manifestations of unilateral lesions, accounting for more than 80%, most in the lower lobe, sometimes only the hilar shadow weight gain, most of them are irregular nebulous cloud-like lung infiltration, from the hilar to the lung field, especially under the lungs The leaves are common, and a few are large leafy solid shadows. The atelectasis is often seen, and often disappears in one place and new infiltration occurs. Sometimes it is bilateral diffuse reticular or nodular infiltrating shadow or interstitial pneumonia. Without the consolidation of the lung segment or the lung lobes, the signs are mild and the chest radiograph is significantly shadowed, which is one of the characteristics of this disease.

4, the course of disease

The natural course varies from 2 to 4 weeks, most of them are feverish from 8 to 12 days, and the recovery period takes 1 to 2 weeks. The X-ray shadow disappears completely, and the symptoms are prolonged for 2 to 3 weeks. .

Examination of mycoplasmal pneumonia in children

Peripheral blood

White blood cell counts are mostly normal, but may increase, but there are also leukopenia.

2. Blood biochemistry

ESR increased, mostly light, moderately increased, anti-"O" antibody titer was normal, some patients with serum transaminase, lactate dehydrogenase, alkaline phosphatase increased.

3.MP detection

Early children can be detected by PCR to detect secretions such as sputum and MP-16SRDNA or P1 adhesion protein genes in lung tissue, and MP can also be isolated from sputum, nasal secretions and throat swabs.

4. Serum antibody detection

Serum antibodies can be determined by complement binding assays, indirect hemagglutination assays, enzyme-linked immunosorbent assays, indirect immunofluorescence assays, or early detection by antigen detection.

5. , nose and throat swab culture

Mycoplasma pneumoniae can be obtained, but it takes about 3 weeks, and anti-serum can be used to inhibit its growth. Negative culture can also be confirmed by hemolysis of red blood cells. About 2 weeks after the onset, about half of the cases produce antibodies.

6. Red blood cell condensation set test

Positive, titration titer is above 1:32, the significance of 4 times increase in recovery period titer is significant, 40-50% of cases of streptococcal MG agglutination test is positive, blood MG streptococcal lectin titer is 1:40 or Higher, it is more meaningful to gradually increase the titer to 4 times.

7. X-ray inspection

X-ray changes are divided into 4 types: 1 with hilar shadow thickening as prominent; 2 bronchial pneumonia changes; 3 interstitial pneumonia changes; 4 uniform solid shadows, slight signs and chest X-ray shadows, is the characteristics of this disease First, sometimes with pleural effusion, the lung X-ray changes faster is also one of its characteristics.

(1) bronchial pneumonia changes more: chest radiographs mostly manifested as unilateral lesions, accounting for more than 80%, most in the lower lobe, sometimes only the hilar shadow weight gain, most of the irregular flaky or cloud-like lung Infiltration, from the hilar to the extension of the lung field, especially in the lower lobe of both lungs, is a change of bronchial pneumonia.

(2) Uniform real shadow: a small number of uniform solid shadows, similar to lobar pneumonia, showing signs of atelectasis; often one has dissipated and new infiltration occurs elsewhere.

(3) Interstitial pneumonia changes: sometimes diffuse reticular or nodular infiltration shadows on both sides, showing changes in interstitial pneumonia, without concomitant changes in the lung segment or lobe.

(4) Hilar shadow thickening: Most children have hilar lymphadenopathy or widened hilar shadow.

8. ECG and B-ultrasound

If necessary, check the ECG and B-ultrasound to determine if there is any myocardial damage or liver damage.

Diagnosis and diagnosis of mycoplasmal pneumonia in children

diagnosis

1 persistent severe cough, X-ray findings are far more significant than physical signs, such as several cases in the elderly, suspiciously epidemic cases, can be diagnosed early.

2 The number of white blood cells is mostly normal or slightly increased, and the erythrocyte sedimentation rate is increased rapidly. The Coombs test is positive.

3 antibiotics, streptomycin and sulfa drugs are ineffective, macrolides are effective.

4 The serum lectin (IgM type) mostly increased to a titer of 1:32 or higher, and the positive rate was 50% to 75%. The higher the positive rate, the higher the positive rate. The cold agglutinin began to appear on the first weekend after the onset. It will reach the peak in the 3rd to 4th week, then decrease, and disappear in 2~4 months. This is a non-specific reaction, which can also be seen in liver disease, hemolytic anemia, infectious mononucleosis, etc., but its titer is generally not More than 1:32, and adenovirus caused pneumonia in older children, and the cold agglutinin was mostly negative.

5 serum specific antibody assay has diagnostic value, clinically used to have complement fixation test, indirect hemagglutination test, indirect immunofluorescence and enzyme-linked immunosorbent assay, etc., Mycoplasma pneumoniae-specific IgM antibody can be on the 3rd day after the disease Elevated, most of the 2 weeks after the disease disappeared (76.5%), ELISA, micro-immunofluorescence (MIF) and other methods for specific IgM detection, specific IgG production is late, can not be used as an early diagnosis, in addition, enzyme-linked adsorption In the past, the detection of antigens by monoclonal antibodies made of Mycoplasma pneumoniae membrane protein has been reported in recent years. In recent years, the use of DNA probes and PCR to detect the Mycoplasma pneumoniae DNA diagnosis has the advantages of sensitivity, rapidity and high specificity, but After mycoplasma infection, it can live in the pharynx for a long time, and sometimes it can be carried. Therefore, the pathogen detected from the throat swab cannot directly represent the lung pathogen, and the blood Mycoplasma pneumoniae does not exist in the carrying state. Therefore, PCR is used to detect Mycoplasma pneumoniae. The sensitivity and specificity are both increased, and the clinical value is large.

6 It takes too long to culture mycoplasma with patient sputum or throat swab. It usually takes 2 to 3 weeks, so it has little clinical help.

Differential diagnosis

The disease must sometimes be identified with the following diseases:

1 tuberculosis

Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis, which can invade many organs. Tuberculosis is the most common form of pulmonary involvement, and it is an important source of infection.

2 bacterial pneumonia

Bacterial pneumonia accounts for 80% of all kinds of pathogen pneumonia in adults. Since the era of antibiotics, the prognosis of bacterial pneumonia has improved significantly, but since the 1960s, the mortality rate has remained high. Currently, some new bacterial pneumonia has emerged. Characteristics, including pathogen spectrum changes, especially the proportion of G-bacteria in hospitals has increased significantly. Although Streptococcus pneumoniae still dominates community-acquired pneumonia pathogens, clinical manifestations tend to be atypical. The trend of increased bacterial resistance.

3 whooping cough

Pertussis (whooping cough) is a common acute respiratory infection in children. Bordetella pertussis is the causative agent of this disease. It is characterized by paroxysmal spasmodic cough, with a special inhalation snoring at the end of the cough. The course of the disease is long, up to several weeks or even 3 months, so it is called pertussis. Young children suffering from this disease are prone to suffocation, pneumonia, encephalopathy and other complications, and high mortality. In recent years, the incidence of infants and adults has increased.

4 typhoid fever

Typhoid fever is an acute intestinal infectious disease caused by typhoid bacillus, with persistent bacteremia and toxemia, proliferative response of the mononuclear phagocytic system, hyperplasia and swelling mainly in the lower ileum lymphoid tissue. Necrosis and ulceration are the basic pathological features. Typical clinical manifestations include persistent high fever, systemic toxic symptoms and gastrointestinal symptoms, relatively slow pulse, rose rash, hepatosplenomegaly, and leukopenia. This disease is also known as intestinal fever. Enteric fever). However, the clinical manifestations of this disease are mainly caused by the spread of pathogens through the blood to the whole body.

5 infectious mononucleosis

Infectious mononucleosis is an acute mononuclear-macrophage system proliferative disease caused by EB virus infection, and the course of disease is often self-limiting. Clinical manifestations of irregular fever, lymphadenopathy, sore throat; laboratory tests can be found in peripheral blood mononuclear cells significantly increased, abnormal lymphocytes, heterophilic agglutination test and anti-EBV antibody positive.

6 interstitial pneumonia

Mostly due to viruses, mainly adenovirus, respiratory syncytial virus, influenza virus, parainfluenza virus, measles virus and so on. Among them, interstitial pneumonia caused by adenovirus and influenza virus is more common and more serious, often forming necrotizing bronchitis and bronchial pneumonia, and the course of disease is prone to become chronic pneumonia.

Can be identified according to medical history, tuberculin test, X-ray follow-up observation and bacteriological examination and serological reaction.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.