(A) Definition: Cough is the main or only clinical manifestation, with a duration of >4 weeks and no significant abnormalities on chest X-ray. Age characteristics: The clinical diagnosis of chronic cough in children should take into account the age factor, which is an important feature that distinguishes children from adults. 1. cough variant asthma (CVA): CVA is the most common cause of chronic cough in children in China, especially in preschool and school-age children. Clinical features and diagnostic clues of CVA: (1) persistent cough >4 weeks, usually dry, often at night and/or early in the morning, aggravated by exercise and cold air, with no clinical signs of infection or ineffective after prolonged antimicrobial therapy; (2) significant relief of cough symptoms with diagnostic bronchodilator therapy; (3) normal pulmonary ventilation, with bronchial excitation tests suggesting airway hyperresponsiveness ; (4) a history of allergic disease, as well as a positive family history of allergic disease. A positive allergen test may assist in the diagnosis; (5) except for chronic cough caused by other diseases. 2. Upper airway cough syndrome (UACS): UACS is the second leading cause of chronic cough in children, especially in preschool and school-age children. Until 2006, the diagnostic name for UACS was postnasal drainage syndrome (PNDs). The clinical features and diagnostic clues of UACS: (1) persistent cough >4 weeks with white foamy sputum (allergic rhinitis) or yellow-green pus sputum (sinusitis), cough worse in the morning or with position change, accompanied by nasal congestion, runny nose, dry throat with foreign body sensation and repeated clearing of the throat; (2) marked follicular hyperplasia in the posterior pharyngeal wall, sometimes cobblestone-like changes are seen, or mucus-like or purulent secretions are seen attached; (3 ) antihistamines, leukotriene receptor antagonists and nasal glucocorticoids are effective for chronic cough caused by allergic rhinitis, and chronic cough caused by purulent sinusitis requires antibacterial medication for 2 to 4 weeks; (4) nasopharyngolaryngoscopy or lateral head and neck films, sinus X-rays or CT films may be helpful for diagnosis. 3, (respiratory) post-infection cough (PIC): PIC is a common cause of chronic cough in young children and preschoolers and has the highest diagnostic revision rate among the causes of chronic cough in children Heart 0J [Liang]. clinical features and diagnostic clues of PIC: (1) a recent history of definite respiratory infection; (2) cough lasting >4 weeks that It is an irritating dry cough or accompanied by a little white mucous sputum; (3) chest radiography is not abnormal or only shows increased texture in both lungs; (4) normal pulmonary ventilation or presents a transient airway hyperresponsiveness; (5) cough is usually self-limiting; if the cough lasts for more than 8 weeks, other diagnoses should be considered; (6) except for other causes of chronic cough. 4. Gastroesophageal reflux cough (GERC): GERC has been reported to account for 4.7% to 24% of chronic cough in children in China. “The composition ratio study reported only 0.62% of GERC, but 30.77% of cases with 24-hour lower esophageal pH monitoring. 24-hour lower esophageal pH monitoring is the gold standard for diagnosing GERC, but it is difficult to perform and/or parents do not agree to perform this invasive procedure. This may underestimate the prevalence of GERC in China, and it is not possible to conclude that GERC is rare in China without such monitoring. It is important to note that prolonged coughing may also lead to GERC in children. The clinical features and diagnostic clues of GERC in children are: (1) paroxysmal cough is best at night; (2) cough may also worsen after eating; (3) positive 24-hour lower esophageal pH monitoring; (4) chronic cough from other causes is excluded. 5. psychogenic cough: ACPP recommends that psychogenic cough in children should be diagnosed only when multiple tics are excluded and the cough improves with behavioral interventions or psychotherapy, and is commonly seen in school-age and adolescent children. Clinical features and diagnostic clues of psychogenic cough: (1) it is more common in older children; (2) it is predominantly a daytime cough that disappears when focused on a particular event or at night rest, and may be a goose-like, high-pitched cough; (3) it is often accompanied by symptoms of anxiety but not organic disease; and (4) it excludes other causes of chronic cough. 6. Other causes of chronic cough: (1) non-asthma eosinophilic bronchitis (NAEB): Gibson first reported NAEB in 1989, accounting for 13.5% of the causes of chronic cough in adults, and the Composition Ratio Study reported NAEB accounts for only 0.57% of the cases reported in the “Composition ratio study”, and such a low composition ratio needs to be considered, perhaps related to the fact that sputum induction techniques and eosinophil counts are not yet widespread in domestic pediatrics. Clinical features and diagnostic clues of NAEB: (1) irritant cough lasting >4 weeks; (2) normal chest X-ray; (3) normal pulmonary ventilation and no airway hyperresponsiveness; (4) relative percentage of eosinophils in sputum >3%; (5) ineffective treatment with bronchodilators and effective treatment with oral or inhaled glucocorticoids; (6) chronic cough except for other causes. (2) Allergic (allergic) cough (atopic cough, AC): clinically, some children with chronic cough have atopic constitution and effective treatment with antihistamines and glucocorticoids, but they are not bronchial asthma, CVA or NAEB, etc. This type of cough is called allergic (allergic) cough in the literature. AC clinical features and diagnostic clues: (1) cough lasting >4 weeks with an irritating dry cough; (2) normal pulmonary ventilation and negative bronchial excitation test; (3) increased sensitivity of cough receptors; (4) history of other allergic diseases, positive allergen skin test, and elevated total and/or specific serum IgE; (5) chronic cough from other causes excluded. (3) Drug-induced cough: Although uncommon in children, they should still be alerted. Drugs such as angiotensin-converting enzyme inhibitors and β-adrenergic receptor blockers, such as benztropine, can induce chronic cough, which usually manifests as a persistent dry cough, aggravated at night or when lying down, and which is significantly reduced or even disappears 3-7 d after stopping the drug. (4) Otogenic cough: 2% to 4% of the population has an auricular branch of the vagus nerve (arnold nerve), and when lesions occur in the middle ear, stimulation of the vagus nerve can cause a chronic cough. Otogenic cough is a rare cause of chronic cough in children. 7. Multiple causes of chronic cough: It is important to note the complexity and variability of the causes of chronic cough in children, some of which overlap with each other. “The Composition Ratio Study reported that children with chronic cough of multiple etiologies accounted for 8.54% of the total eligible cases, especially UACS combined with CVA, which accounted for 50.13% of multi-cause cases, followed by PIC combined with UACS (26.10%).