Primary ciliary dyskinesia in children

　　First, Etiology

　　1, Congenital abnormality

　　Primary ciliary dyskinesia, cystic fibrosis, Young syndrome, abnormal cilia length, cilia absence, short dynein arm deficiency, complete or partial absence, radial spoke defect, and microtubule ectopia, etc.

　　2, Acquired laterally

　　Local abnormalities are mostly secondary. Chronic tracheitis, pneumonia, bronchiectasis, asthma, and lung cancer can cause unequal cilia size and giant cilia; chronic sinusitis and asthma can cause axoneme变性; viral infection can cause cilia shedding and concave; allergic rhinitis can cause cilia weakness; the secretion of hydrogen peroxide by Mycoplasma pneumoniae and the secretion of green脓毒素 by Pseudomonas aeruginosa can inhibit ciliary movement, smoking, environmental pollution, radiation, hydrogen sulfide, mechanical ventilation, and other factors can cause clearance dysfunction. Clinical diseases caused by ciliary dysfunction are extensive, involving all parts with cilia distribution, with respiratory tract infections caused by airway ciliary dysfunction being the most common; ciliary dysfunction in sperm flagella, vas deferens, and fallopian tube can lead to infertility or sterility; ciliary dysfunction in the middle ear and paranasal sinuses can lead to otitis media and sinusitis; dysfunction of rod cells in the retina, hair cells in the vestibule, and olfactory cells can lead to blindness, deafness, and olfactory disorders; there are also reports of hydrocephalus due to ciliary dysfunction in the brain and spinal cord ependyma.

　　Second, Pathogenesis

　　Many parts of the human body have cilia or similar structures. The normal function of cilia is an important factor in maintaining the function of the organ, system, and even the entire human body; the normal function of the airway mucus-cilia transport system is of great significance in maintaining the defense function of the airway. Cilia structures are widely present in respiratory tract, middle ear, fallopian tube, vas deferens, sperm flagella, as well as in the brain, spinal cord ependyma, and other tissues and organs. Due to abnormal cilia structure and function, poor ciliary movement and clearance dysfunction can cause recurrent sinusitis, bronchitis, pneumonia, otitis media, ectopic pregnancy, infertility, and hydrocephalus. Abnormal ultrastructure of cilia shows more than 20 types, mainly involving defects in the dynein arm, missing microtubules, defective radial spokes, and disordered microtubule arrangement. Further ciliary biopsy is needed to assist in diagnosis. Since the cilia structure is composed of at least more than 200 proteins, with a large number of potential genes, it is unlikely that gene detection will be used as a diagnostic tool in the short term. Abnormal cilia include: ciliated cells exist on the surface of the protein dynein arm, and cilia are also distributed in the paranasal sinuses, auditory tube, middle ear, and other places. In addition, cilia structures are also present in the fallopian tube, sperm, and ependyma of the brain and spinal cord. The distribution of cilia in the bronchi of the airway is different, with the largest in the large airways and fewer in the small airways; there are no cilia structures in the alveolar sacs and alveoli. Each ciliated cell has more than 200 cilia, with a diameter of about 0.1-0.2 μm and a length of about 3-7 μm. Each cilium includes the body, base, and crown, and the cross-section appears circular under the electron microscope, with a pair of central microtubules in the center and nine pairs of peripheral microtubules evenly surrounding them, known as the 92 axoneme microtubule structure.

　　It can cause recurrent sinusitis, bronchitis, pneumonia, otitis media, ectopic pregnancy, infertility and sterility, and hydrocephalus, etc. Recurrent upper and lower respiratory tract infections, including recurrent otitis media, sinusitis, bronchitis, pneumonia, and symptoms of bronchial dilation. Common symptoms include otorrhea, purulent nasal discharge, cough, expectoration, hemoptysis, and in severe cases, dyspnea and stridor. Cyanosis and clubbing of the fingers. Children with dextrocardia should consider the possibility of concomitant bronchial dilation and sinusitis if they have frequent upper respiratory tract infections and pneumonia, which may indicate Kartagener syndrome. If only visceral transposition and bronchial dilation are present, it is an incomplete Kartagener syndrome. Kartagener syndrome often coexists with other congenital malformations, the most common being congenital heart disease, hydrocephalus, cleft palate, biconcave cervical ribs, anal atresia, hypospadias, and duplicated kidneys. Other conditions include membranous pupil, intellectual disability, hearing impairment, and olfactory defect, etc.

　　The onset age can range from infancy to adulthood, but it is more common in school-age children and young adults, and it is a recurrent upper and lower respiratory tract infection that worsens with age, including recurrent otitis media, sinusitis, bronchitis, pneumonia, and symptoms of bronchial dilation. Common symptoms include otorrhea, purulent nasal discharge, cough, expectoration, hemoptysis, and in severe cases, dyspnea and stridor. It is often misdiagnosed as common chronic bronchitis, chronic pneumonia, asthma, and tuberculosis. Common signs include cyanosis and clubbing of the fingers. Bronchography shows bronchial dilation, with the lower lobes being the most common, followed by the lingula of the left lung and the middle lobe of the right lung. The most common morphology is columnar dilation, and a few cases show cystic dilation. Sometimes it can be accompanied by atelectasis and emphysema, hearing impairment, male infertility, and 50% of patients have dextrocardia.

　　There is no significant gender difference, but there is a family hereditary tendency, which can occur in the same generation or in the next generation. Their parents often have a history of consanguineous marriage, and they often exist simultaneously with other congenital malformations (such as atrial septal defect). Strengthen prenatal care. After birth, actively prevent upper respiratory tract infections, and use antibiotics for respiratory tract infections until complete recovery. Good immunity to measles and pertussis and other autoimmune diseases. During the non-infection period, antibiotics can be used to prevent infection, and proper treatment can enable patients to have a normal lifespan.

　　1. General examination

　　Commonly, there are signs of infection, such as anemia and hypoxemia,

　　2. Electron microscopy examination

　　The diagnosis can be made by taking a biopsy of the nasal mucosa or bronchoscopic biopsy of the bronchial mucosal epithelium, observing the number and structure of cilia under an electron microscope to confirm the diagnosis, and checking the sperm swimming ability can be helpful for auxiliary diagnosis.

　　3. Imaging Examination

　　Changes such as pulmonary inflammation shadow, bronchitis, pneumonia, sinusitis, bronchiectasis, etc., sometimes accompanied by atelectasis and emphysema; bronchography or high-resolution CT shows that bronchiectasis is most common in the lower two lobes, followed by the lingular lobe of the left lung and the middle lobe of the right lung, with columnar expansion being the most common, a few cases of cystic expansion, and sometimes a dextrocardia can be seen.

　　4. Methods of examination for mucociliary clearance function

　　Including saccharin screening test, radioactive aerosol inhalation lung scan, scanning electron microscopy combined with high-speed photography technology to measure ciliary beating frequency, fiberoptic bronchoscopy combined with gamma photography technology to measure bronchial mucus transport speed.

　　According to the age characteristics of the child, provide nutrition-rich and easy-to-digest food. Breastfeeding children should take milk as the main food and can drink some water appropriately. Milk can be diluted with a little water to make it thinner, feed less each time, and increase the frequency of feeding. If milk is aspirated, it should be cleared from the nostrils in time. Children who are older and can eat can eat nutritious, easy-to-digest, light foods, eat more fruits and vegetables, and drink more water.

　　1. Treatment

　　For the treatment of PCD, active anti-infection should be carried out during the acute stage of infection, with strengthening of back blows and postural drainage to promote sputum excretion, in order to protect lung function and avoid the occurrence of pulmonary heart disease as much as possible. Treatment is the same as general bronchiectasis, mainly symptomatic treatment, with anti-infection as the main treatment, and atomization inhalation for expectoration and postural drainage as auxiliary. Bronchodilators relieve wheezing and airway obstruction, otolaryngology treats sinusitis and otitis media, and at the same time, other infections should be prevented. Such as measles, influenza, etc., avoid air pollution and smoking. During the remission period, the focus is on enhancing resistance. Children with bronchiectasis often have yellow-green sputum, which is mostly caused by Gram-negative bacilli such as Pseudomonas aeruginosa, so empirical ceftriaxone or imipenem/cilastatin sodium (Tienam) should be used for anti-infection after admission.

　　2. Prognosis

　　If diagnosed early and appropriate prevention and treatment measures are taken, the prognosis is still good. Recurrent infectors often die of congestive heart failure.