ORLANDO, Fla. — Asthma is the most common cause of chronic cough in children, but it’s important to be aware of other differential diagnoses for those patients who have less common concerns, according to Rajeev Bhatia, MD, division chief of pulmonology at Phoenix Children’s in Phoenix, Arizona. Bhatia reviewed both the major causes of chronic cough as well as the rare zebras to watch out for in a presentation at the American Academy of Pediatrics (AAP) 2024 National Conference.

“When you see a patient for cough, the most important thing is, history, history, history,” Bhatia said. “There are many, many, many clues in the history, age of onset, and duration.” That includes starting at birth to ensure you don’t miss key details such as a preterm birth. It’s also important to discuss what the cough sounds like, how frequent it is, what makes it better, what makes it worse, and how it’s affecting the child and others around them — all of which can help narrow the diagnosis.

Jose Quijada, DO, a pediatrician with CommuniCare Pediatrics in San Antonio, found the session “incredibly useful” not only because of the specific pointers about each condition but also because of the realistic case studies he included throughout.

“Sometimes when you’re practicing, you focus on what’s most common,” Quijada said, so it was helpful to get a review of some of the key features and red flags that point to less common causes that may need to be considered. He particularly appreciated the discussion of habitual cough and potential treatments because those can be challenging patients and it can be tough to find a middle ground with how much workup to do.

Common Causes of Chronic Cough

The coughing from inadequately controlled asthma tends to be nonproductive and worse at night or in the early morning, Bhatia explained, and it’s often accompanied by wheezing, shortness of breath, and chest tightness. While fractional exhaled nitric oxide can be useful, “studies show that it is more useful for to monitor the symptoms rather than to diagnose the asthma,” Bhatia told attendees, but he also added that spirometry can be normal in patients with asthma. In young patients, the Asthma Predictive Index can be an invaluable tool, he also said.

Another common cause of chronic cough is a postinfectious cough, which lasts more than 3 weeks after resolution of acute upper respiratory infection. It occurs in about one in 10 children after a viral infection such as a rhinovirus or respiratory syncytial virus infection and results from extensive inflammation and disruption of the airway epithelial integrity. Chest x-rays are usually normal in these patients, and the cough will usually resolve on its own. Albuterol is not any more effective than placebo for a postinfectious cough, and antibiotics similarly have no clinically useful role.

A wet cough that lasts for at least 4 weeks and appears to have no other specific cause may be protracted bacterial bronchitis (PBB). While the cause of PBB isn’t known, it could be due to frequent illnesses that cause airway inflammation and injury over time, thereby making it easier for bacteria to grow and cause infection. Risk factors include tracheomalacia/bronchomalacia and childcare attendance, and typical pathogens include Haemophilus influenzae, Streptococcus pneumonia, and Moraxella catarrhalis.

While an x-ray can be done, radiography is often normal in patients with PBB. Bronchoscopy will reveal purulent secretions. PBB should resolve with at least 2 weeks of antibiotics, including amoxicillin-clavulanate, but the course can be extended to 4 weeks if the cough persists. However, about 40% of patients will have recurrence, and those with recurrent PBB or with a chronic cough unresponsive to 4 weeks of antibiotics should be referred to a pediatric pulmonologist.

Upper airway cough syndrome is the updated name for postnasal drip, which can occur with both allergic and nonallergic rhinitis and chronic rhinosinusitis. This is often a dry, throat-clearing cough that can be accompanied by headaches, nasal congestion, and sinus or facial tenderness. An examination will reveal posterior pharynx cobblestoning, Bhatia said, and empirical use of intranasal steroids can be both diagnostic and therapeutic for upper airway cough syndrome. He also emphasized the importance of taking an environmental history and avoiding exposure of environmental triggers.

Uncommon Pulmonary Causes of Chronic Cough

After discussing frequent reasons patients may present with a chronic cough, Bhatia went on to discuss the less common things to consider if the provider has eliminated the other possibilities. These include both pulmonary causes as well as congenital malformations, gastrointestinal causes, and habit cough.

A child who presents with a sudden onset of cough or wheeze in the absence of an upper respiratory infection may have a retained foreign body. This cough can be mistaken for bronchiolitis, asthma, croup, and other infectious conditions, especially because a partial obstruction can make diagnosis confusing or challenging. Adding to the challenge is that most foreign bodies will be radiolucent. A decubitus chest x-ray could be useful, but bronchoscopy is necessary for diagnosis. Bhatia stressed that it’s easy to miss a foreign body in younger children and that the wheezing can be more prominent on one side or another.

Cystic fibrosis, another uncommon cause of chronic cough, is ideally diagnosed via newborn screening, but screening is imperfect and can involve missed diagnoses or false negatives. Over 75% of cystic fibrosis cases are diagnosed by age 2, but that means a substantial number of cases still are not diagnosed until older childhood or later. This cough will be a chronic productive/wet cough.

A family history of cystic fibrosis may be present but doesn’t have to be, so signs to look for include poor weight gain, sinusitis, nasal polyps, clubbing, and isolation of suspicious organisms from a respiratory culture, such as Pseudomonas aeruginosa or Burkholderia cepacia complex. Clubbing in the fingers is a particularly telltale symptom of undiagnosed cystic fibrosis, and bronchiectasis of unknown etiology will be present. Suspicion of cystic fibrosis should lead to a referral to a cystic fibrosis center for a sweat test.

Even rarer than cystic fibrosis is primary ciliary dyskinesia (PCD), an inherited autosomal recessive disease that occurs in about one in 20,000 live births and involves a structural or functional defect in the cilia. About half of all patients with PCD will have situs inversus — an arrangement of chest and abdominal organs that is a mirror image of typical human anatomical presentation — but most people with situs inversus do not have PCD. One type of PCD is Kartagener syndrome, identified by the triad of situs inversus totalis, chronic sinusitis, and bronchiectasis.

Children with PCD present with a chronic productive cough and recurrent pneumonias, and nearly all patients will have rhinosinusitis. About 60% of patients will develop respiratory symptoms such as mild distress or cough in their first month, and recurrent otitis media is common in these patients. PCD diagnosis is based on a combination of genetic testing, nasal nitric oxide, and evaluation of ciliary motion and structure. Clinical suspicion of PCD should lead to a specialist referral.

Nearly all people with PCD will eventually develop bronchiectasis, where the priority should be airway clearance using antibiotics for acute exacerbations and chronic azithromycin therapy for recurrent exacerbations. Patients with chronic rhinosinusitis, chronic otitis media, and nasal polyposis should be referred to an ENT specialist.

Other Uncommon Causes of Chronic Cough

A non-pulmonary, uncommon cause of chronic cough is a vascular ring, a congenital anomaly in which blood vessels encircle and potentially constrict the esophagus and/or trachea. The most common type is a double aortic arch, but a right aortic arch or pulmonary artery sling is also possible. These coughs sound harsh and are usually accompanied by stridor, dyspnea and feeding problems. Workup includes an echocardiogram, a CT angiogram, and possibly a bronchoscopy to determine the extent of the airway narrowing. In symptomatic patients, surgery is indicated for correction.

Another congenital malformation that can cause chronic cough is a tracheoesophageal fistula, which occurs in about one in 3500 live births, commonly linked to trisomy disorders and VACTERL. Several types of tracheoesophageal fistula exist, and H-type fistula is associated with late onset symptoms. The cough can be wet or dry and sometimes sounds like barking because of the associated airway collapse. Patients often have recurrent pneumonia, bronchitis, and cough or cyanosis with feeding. Workup should include an upper gastrointestinal series but not with barium, Bhatia said, because that can cause pneumonitis. Instead, the series should be done with a thickened water-soluble contrast material, and a bronchoscopy may be indicated as well.

Though common as a condition in adults, gastroesophageal reflux disease (GERD) is a rare, but possible, cause of chronic cough in children. More often, the reflux is the result of the cough rather than the cause. The most sensitive tool for assessing GERD is esophageal 24-hour pH/impedance reflux monitoring. However, treatment of the reflux for cough is not recommended unless the patient has clinical features of GERD, including dystonic neck posturing in infants, heartburn, regurgitation, or other symptoms. If the patient has clinical symptoms, then treatment is acid suppressive therapy for 4-8 weeks, followed by a clinical reassessment.

An uncommon cause of chronic cough with no biological mechanism is habitual cough. Habit cough is most easily distinguished from other coughs by its sounds, a “large, loud, honking noise,” Bhatia said. It also lacks a clear trigger and is usually absent during sleep, but it can be continuous during the day. Frustratingly, the patients themselves often don’t seem bothered by the cough, but “it’s very disruptive in the school and everywhere else,” Bhatia said. Families and/or providers will often have tried multiple treatments and seen no improvement with habit cough.

The first thing to do with a habit cough is reassure the family that there’s nothing serious going on because they are often worried by this point. Several non-pharmaceutical treatments can be effective, such as suggestion therapy or the “warm water technique,” in which the patient takes a sip of warm water every time they feel the urge to cough. “If they’re able to break the cycle, most of the time, they are fine,” Bhatia said. In rarer cases, more involved behavioral interventions may be indicated, such as a psychology referral if an underlying anxiety or other behavioral disorder is contributing.

Newer Causes of Cough

Two more recent causes of cough to watch for are long COVID and e-cigarette or vaping product–associated lung injury (EVALI), Bhatia said. The clearest sign of EVALI is a history of e-cigarette/vaping exposure, but clinical symptoms include a dry cough that occurs with dyspnea and chest pain. A chest x-ray may show diffuse, hazy, or consolidative opacities. Sometimes antibiotics or steroids can be helpful, but the evidence isn’t strong, and the most effective treatment is stopping e-cigarette use. Less commonly, passive exposure to vaping can also be associated with EVALI.

The most recent research on long COVID suggests that about 10-20% of children with acute COVID develop long COVID, and about a quarter of these patients develop a chronic dry cough. It’s often associated with fatigue and shortness of breath, which can be assessed with cardiopulmonary exercise testing. Sometimes a short trial of inhaled steroids can help.

Bhatia also mentioned a handful of other uncommon causes of chronic cough that most American pediatricians are unlikely to see: Childhood interstitial lung disease, tuberculosis, use of Angiotensin-Converting Enzyme inhibitors, and a build-up of ear wax via the Arnold’s nerve reflex.

Evaluation and Workup

Bhatia also discussed what to cover while taking a history and questions to ask. The history should include the type of cough, the onset timing (sudden vs gradual), associated symptoms, the cough trajectory, medications the patient is taking, and the patient’s past medical history and environmental exposures. Those attributes are included in this more comprehensive list of questions to consider during evaluation, adapted from a list provided in a 2019 article in Paediatric Respiratory Reviews:

• Age of onset and duration?
• Was the onset sudden or associated with an illness?
• Is the cough wet or dry?
• What does the cough sound like?
• How often does the cough occur?
• Is it progressive?
• Is it present during sleep?
• Are there any other associated symptoms, such as wheezing, dyspnea, vomiting, chest pain, etc?
• Are there any exacerbating factors or known triggers?
• Are there any relieving factors, including a trial of bronchodilators?
• Has there been exposure to auto-irritants, such as secondhand smoke?
• What is the cough’s effect on the child and others around the child?
• Does the child have any other underlying conditions such as neuromuscular disease or asthma?
• What medications is the child taking or has recently taken?
• Is there a family history of atopy and/or respiratory disease?

Bhatia also recommended paying special attention to the following red flags or key features that may help more quickly narrow the diagnosis and often require a specialist referral:

• Digital clubbing, failure to thrive, or low-tone
• An abnormal cardiac exam
• Tachypnea, hypoxemia, chest retractions, or hemoptysis
• Abnormal breath sounds such as unilateral wheezing or coarse crackles
• Abnormal spirometry in those aged 5 and older showing reversible obstruction, which often indicates asthma
• An abnormal chest x-ray with, for example, bilateral infiltrates, hyperinflation, right middle lobe syndrome, situs inversus, unilateral hyperlucency, a right aortic arch, etc.

No external funding was used for the presentation. Bhatia and Quijada had no disclosures.

Tara Haelle is a Dallas-based science journalist.