1. Common causes and treatments of chronic cough Chronic cough is a common clinical problem and is the most common symptom seen in respiratory medicine. China’s cough diagnosis and treatment guidelines classify cough into acute cough, subacute cough and chronic cough according to the duration of cough, and chronic cough refers to cough for more than 8 weeks, with cough as the only symptom, ineffective treatment with antibiotics and no abnormal findings on routine chest X-ray, i.e. chronic cough of unknown origin cough. There are many clinical causes of unexplained chronic cough, the common ones are as follows: upper airway cough syndrome (UACS), cough variant asthma (CVA), non-asthmatic eosinophilic bronchitis (NAEB), gastroesophageal reflux (GERD), etc. By taking medical history, pulmonary function test, bronchial excitation test, allergen test, induced sputum test, 24h esophageal PH test, etc. Most of the relevant tests can clarify the etiological diagnosis, and the corresponding etiological treatment and symptomatic treatment can significantly improve the cough symptoms. In primary care hospitals where relevant tests are not available, a suspicious diagnosis can sometimes be made based on the characteristics of the medical history and diagnostic treatment can be given, which can be disproved if the symptoms improve significantly after treatment. For chronic cough due to UACS, CVA, and NAEB, the onset of which is related to chronic inflammation of the airways, anti-inflammatory therapy targeting airway inflammation can be given, including inhaled glucocorticoids, short-term oral glucocorticoids, and leukotriene modulators; for UACS, antihistamines, decongestants, and nasal hormones should still be given; for GERD, acid-control agents should be given. If the symptoms do not improve with diagnostic treatment, the original diagnosis should be considered wrong and further examinations, including chest CT and fibrinoscopy, should be performed in time to clarify the etiological diagnosis. 2. Cough variant asthma accounts for only 25% of chronic coughs In the past, chronic coughs commonly found in clinical settings were often misdiagnosed as chronic bronchial, bronchitis, pharyngitis, etc., and given large amounts of antibiotic treatment or only general cough suppressants, resulting in coughs that could not be relieved and patients repeatedly seeking medical attention, making coughs persistent and a headache for both patients and physicians. Since the publication of the first guidelines for the diagnosis and treatment of chronic cough in the United States in 1998, the global understanding and level of diagnosis and treatment of chronic cough has improved significantly, and the publication of the guidelines for the diagnosis and treatment of cough in China in 2005 has further standardized and improved the level of diagnosis and treatment of chronic cough in China. Nowadays, clinicians have realized that chronic cough is not always the common chronic bronchitis, bronchitis, pharyngitis, etc. Many etiologies can cause chronic cough and treatment for the etiology can bring the cough under control. This treatment has indeed led to cough control in some patients. However, CVA accounts for only about 25% of the causes of chronic cough, and not all chronic coughs of unknown origin are CVA; for example, a patient with a suspected external diagnosis of CVA who has been ineffective with inhaled glucocorticoids or even oral hormones should not be limited to the original diagnosis and should undergo further relevant investigations as soon as possible to clarify the etiological diagnosis to avoid delay. This patient had developed intrapulmonary tuberculosis foci due to multiple oral prednisone doses, but no abnormal findings were found when the chest radiograph was taken at the beginning of the disease. When multiple etiologies coexist, multiple etiologies should be treated simultaneously. Chronic cough can have a single etiology or two or three etiologies at the same time, making clinical diagnosis and treatment of the etiology more complex and difficult. According to a foreign survey, about 16% of chronic coughs are caused by two causes and about 1% by three causes at the same time, commonly UACS, CVA and GERD can co-exist in one patient and together cause the cough. In this group of patients, antihistamines or nasal hormones should be given to treat UACS, and inhaled hormones should be given to treat CVA, and acid suppressants should be given to GERD. The cough was characterized by dry cough, obvious at night, easy to cough when smelling irritating odor or cold air, accompanied by nasal congestion, runny nose and sneezing, and a positive bronchial excitation test, which led to the diagnosis of UACS and CVA. The patient’s symptoms did not improve significantly and he still had a severe cough. At another follow-up visit, the patient’s medical history was taken carefully and it was found that the patient had acid reflux and belching and the presence of GERD was suspected. Therefore, clinically, for chronic cough with multiple etiologies coexisting, multiple etiologies should be treated simultaneously. 4. Effects of chronic cough on patients Chronic cough that does not heal over a long period of time can have a great impact on the patient’s mind and body. Cough can lead to general malaise, fatigue, insomnia, muscle pain, hoarseness, vomiting, urinary incontinence, and violent coughing can also lead to rib fractures and fainting, as well as fear of malignant tumors due to coughing. Therefore, in addition to emphasizing the treatment of the cause of the cough, appropriate symptomatic treatment should be given. 5. Chronic cough is easily misdiagnosed and has rare causes In addition to the common causes mentioned above, chronic cough should also take into account rare causes and cases that are easily misdiagnosed or missed, such as the above example of endobronchial tuberculosis, which is not uncommon in China. In addition, inhaled hormone therapy for asthma is ineffective, and even oral hormone therapy is ineffective. This situation can basically overturn the previous diagnosis of CVA, and further chest CT and fibrinoscopy should be performed as soon as possible. Therefore, in clinical practice, careful chest auscultation is very important in chronic cough and can sometimes reveal clues to the diagnosis. In addition, do not give oral hormones in undiagnosed cases to avoid delaying the diagnosis or even leading to exacerbation of the disease. The case cited in this article is a typical case of tuberculosis spreading to the lungs due to the lack of timely anti-tuberculosis treatment for endobronchial tuberculosis and repeated oral hormone administration. Other cases, such as benign and malignant endobronchial occlusions, may also be associated with cough only, with no abnormal findings on chest radiograph. There are also chronic coughs due to smoking that are often overlooked by physicians and patients. Therefore, patients with smoking coughs should first be actively advised to quit smoking while undergoing routine investigations and targeted treatment.