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.