1. Respiratory tract infections and post-infection cough.
Respiratory infections caused by many pathogenic microorganisms such as Mycobacterium pertussis, Mycobacterium tuberculosis, viruses (especially respiratory syncytial virus, parainfluenza virus, and cytomegalovirus), Mycoplasma pneumoniae, and Chlamydia are common causes of chronic cough in children, mostly in preschool children <5 years of age.
Acute respiratory infections with cough symptoms lasting more than 4 weeks can be considered post-infectious cough. The mechanism may be disruption of airway epithelial integrity and/or squamification of ciliated columnar epithelial cells and/or persistent airway inflammation with temporary airway hyperresponsiveness as a result of the infection. The clinical features and diagnostic clues of post-infectious cough are.
(1) A recent history of definite respiratory tract infection ;
(2) Cough that is irritatingly dry or with a small amount of white mucous sputum;
(3) No abnormalities on chest x-ray;
(4) normal pulmonary ventilation;
(5) The cough is usually self-limiting;
(6) Other causes of chronic cough are excluded. If the cough lasts longer than 8 weeks, other diagnoses should be considered.
2. Cough variant asthma (CVA).
Cough variant asthma, also known as allergic cough, is one of the most common causes of chronic cough in children, with cough as the only or main manifestation, without significant wheezing.
The clinical features and diagnostic clues of cough variant asthma are.
(1) Cough lasting >4 weeks, often with episodes or exacerbations at night and/or early in the morning, with a predominantly dry cough;
(2) No clinical signs of infection or ineffective with prolonged antibiotic therapy;
(3) Diagnostic treatment with anti-asthmatic drugs is effective;
(4) other causes of chronic cough are excluded;
(5) Positive bronchial excitation test and/or PEF daily variability (continuous monitoring for 1 to 2 weeks) ≥ 20%;
(6) History of atopic diseases such as eczema, allergic rhinitis or asthma, or positive allergen test, either personally or in first- or second-degree relatives.
Items 1 to 4 above are the basic conditions for diagnosis.
3. Upper airway cough syndrome (UACS).
Various rhinitis (allergic and non-allergic), sinusitis, chronic pharyngitis, chronic tonsillitis, nasal polyps, adenoid hypertrophy and other upper airway diseases can cause chronic coughing, which was previously diagnosed as postnasal drip (flow) syndrome, referring to coughing caused by nasal secretions flowing backwards through the postnasal orifice to the pharynx. The name “postnasal drip syndrome” is now usually replaced by “upper airway cough syndrome”.
The clinical features and diagnostic clues of upper airway cough syndrome are.
(1) Chronic cough with or without sputum, the cough is worse in the early morning or when the position is changed, often accompanied by nasal congestion, runny nose, dry throat with foreign body sensation, repeated clearing of the throat, and a feeling of mucus adherence to the posterior pharyngeal wall; a few children complain of headache, dizziness, and low-grade fever;
(2) Examination of the sinus area may have pressure pain, there may be yellowish-white discharge from the sinus opening, the posterior pharyngeal wall follicles are obviously hyperplastic, cobblestone-like, and sometimes the posterior pharyngeal wall mucus-like adhesions can be seen;
(3) Targeted treatment such as antihistamines and leukotriene receptor antagonists, nasal glucocorticoids are effective;
(4) sinusitis, sinus x-ray or CT film can be seen in the corresponding changes.
4. Gastroesophageal reflux cough (GERC).
Gastroesophageal reflux is a physiological phenomenon in infancy and childhood. The incidence of gastroesophageal reflux in healthy infants is 40% to 65%, peaking at 1 to 4 months of age and mostly resolving spontaneously at 1 year of age. It becomes a disease when it causes symptoms and/or is accompanied by gastroesophageal dysfunction, i.e., gastroesophageal reflux disease. The prevalence of GERD in children is about 15%.
The clinical features and diagnostic clues of GERD are.
(1) Paroxysmal cough, sometimes severe, mostly at night;
(2) Symptoms mostly appear after eating and drinking, and feeding is difficult. Some children have epigastric or subxiphoid discomfort, retrosternal burning sensation, chest pain, and sore throat;
(3) In addition to coughing, it can cause asphyxia, bradycardia and a bowed back in infants;
(4) It can lead to stagnant or delayed growth of the affected children.
5. Eosinophilic bronchitis (EB).
Eosinophilic bronchitis was first reported by Gibso in 1989, and a recent prospective study revealed that eosinophilic bronchitis accounts for 13.5% of chronic cough patients in adults. Eosinophilic bronchitis is considered an important cause of chronic cough in adults, but its prevalence in children is unclear [E/B].
The clinical features and diagnostic clues of eosinophilic bronchitis are.
(1) Chronic irritant cough ;
(2) Normal chest x-ray;
(3) Normal pulmonary ventilation without airway hyperresponsiveness;
(4) relative percentage of eosinophils in sputum > 3%; (5) effective oral or inhaled glucocorticoid therapy.
6. Congenital respiratory diseases.
It is mainly seen in infants and children, especially within 1 year of age. Gormley’s study reported that 75% of children with tracheal softening (second only to congenital vascular malformation) exhibit persistent cough, and the mechanism may be related to tracheal softening obstructing the discharge of secretions and terminal bronchial inflammatory injury. The mechanism may be related to the obstruction of secretion drainage by softened airways and inflammatory damage to the terminal bronchi. This condition is often misdiagnosed as asthma.
7. Psychogenic cough.
Psychogenic cough in children can only be diagnosed when tic disorders are excluded and the cough improves after behavioral interventions or psychotherapy; cough features are only suggestive of psychogenic cough and do not have a diagnostic role.
The clinical features and diagnostic clues of psychogenic cough are.
(1) It is more common in older children;
(2) A predominantly daytime cough that disappears when focused on an event or at rest at night;
(3) It is often accompanied by anxiety symptoms;
(4) No organic disease and other causes of chronic cough are excluded.
8. Other etiologies.
(1) Foreign body aspiration: coughing is the most common symptom following aspiration of foreign bodies from the airway, and foreign body aspiration is an important cause of chronic cough in children, especially those aged 1-3 years. Studies have found that 70% of patients with airway foreign body aspiration present with cough, and other symptoms include decreased breath sounds, wheezing, and history of asphyxia. Once the foreign body enters the area below the small bronchus, there can be no cough, i.e. the so-called “silent zone”.
(2) Drug-induced cough: Angiotensin-converting enzyme inhibitors are less commonly used in children, and some children with renal hypertension may have a cough induced by the use of such drugs as captopril. The mechanism may be related to bradykinin, prostaglandin, and substance P secretion. The cough is usually chronic and persistent, aggravated at night or when lying down, and can be significantly reduced or even disappeared after 3-7 d of discontinuation. β-adrenergic receptor blockers such as progesterone can cause bronchial hyperresponsiveness, so they may also lead to drug-induced cough.
(3) Otogenic cough: 2-4% of the population has an auricular branch of the vagus nerve (arnold nerve). In this group, chronic cough is caused by stimulation of the vagus nerve when the middle ear becomes diseased. Otogenic cough is a rare cause of chronic cough in children.