Review Question - QID 217627

This patient presenting with severe nasal congestion, recurrent sinus infections and pneumonia, failure to thrive, nasal polyps, and digital clubbing along with unknown birth and genetic history likely has cystic fibrosis.

Cystic fibrosis is an autosomal recessive disorder caused by a mutation in the cystic fibrosis transmembrane conductance receptor (CFTR) gene. CFTR codes for a chloride transporter that transports chloride extracellularly. Failure of this transporter gene results in overactivity of sodium resorption in the cell, leading to dehydrated mucus in the respiratory tract. This thick mucus allows bacteria to proliferate, causing chronic rhinosinusitis and nasal polyps. Repeated sinus and lung infections lead to poor lung oxygenation, eventually resulting in fingernail clubbing.

Failure of CFTR not only causes problems in the respiratory tract but also causes dysfunction in the digestive tract. The thick secretions affect the pancreas, blocking ducts that carry digestive enzymes from the pancreas to the small intestine, causing poor digestion and
absorption of nutrients (especially fat-soluble vitamins A, D, E, and K), ultimately resulting in failure to thrive. Additionally, the thick intestinal secretions can cause failure to pass meconium in the first 24 hours of life (meconium ileus). Cystic fibrosis is identified on newborn screening, and detection of an elevated sweat chloride concentration is diagnostic.

Di Cicco et al. describe the epidemiology of nasal polyps in children, how their presence in children can indicate underlying inflammatory processes (e.g., cystic fibrosis), and their treatment.

Incorrect Answers:
Answer 2: IgA deficiency may also present with recurrent sinopulmonary infections as IgA plays an important role in the immunity of the respiratory and gastrointestinal tracts. However, most patients with IgA deficiency are asymptomatic. Patients with IgA deficiency do not present with failure to thrive or digital clubbing.

Answer 3: Primary ciliary dyskinesia or Kartagener syndrome is characterized by the classic triad of situs inversus, recurrent sinusitis, and bronchiectasis. This patient presents with an unremarkable cardiac exam with a normal left-sided point of a maximal impulse. The lack of dextrocardia (apex of the heart on the right side of the chest) means that this patient does not have Kartagener syndrome.

Answer 4: Severe allergic rhinitis is an allergic response and can present similarly to a common cold with sneezing, congestion, itchy nose, and sore throat. However, this patient's extremities show digital clubbing and his lung exam shows diffuse, coarse crackles, suggesting a lower respiratory pathology rather than only in the sinuses.

Answer 5: Severe combined immunodeficiency (SCID) presents with recurrent infections, diarrhea, dermatitis, and failure to thrive. This may present similarly to cystic fibrosis; however, with the profound immune impairment and dysregulation found in SCID, most forms of SCID will result in death during early childhood if not recognized. The most common cause of death in children with SCID is opportunistic infections. Children with SCID are also highly susceptible to malignancy and autoimmune disease.

Bullet Summary:
Cystic fibrosis can present with chronic rhinosinusitis, nasal polyps, digital clubbing, and signs of pancreatic insufficiency (e.g., poor growth, deficiency of fat-soluble vitamins).