Chapter 26: PULMONOLOGY

CYSTIC FIBROSIS AND NASAL POLYPS

PEARL: You are guaranteed to see the words “cystic fibrosis” multiple times on the pediatric certification exam. The American Board of Pediatrics expects you to know this disorder well due to its ability to affect multiple different systems. There is minimal bolding in this section because it’s an extremely high-yield topic, and you should know it ALL cold!

CYSTIC FIBROSIS (CF)

Cystic fibrosis (CF) is an autosomal recessive disorder that will be on your test. Children who are carriers of the cystic fibrosis gene are asymptomatic. It results in excessive loss of chloride through sweat and is associated with significant pulmonary, electrolyte, and gastrointestinal problems. The diagnosis is made through a sweat chloride test showing a level of greater than or equal to 60 mmol/L. A list of the many associations with this disease by category is located below.

• MNEMONIC: If sweat test ≥ 60 mmol/L = “6-tic fibrosis” = diagnostic.
• PULMONARY SYMPTOMS: Diffuse cysts/fibrosis (hence the name), bronchiectasis, hemoptysis, pneumonias (Staphylococcus aureus, Pseudomonas, Haemophilus influenzae), chronic sinusitis, nasal polyps, pneumothorax, Burkholderia cepacia noted in sputum cultures, Pseudomonas pneumonias (and colonization).
  • PEARLS:If Burkholderia cepacia is mentioned, go to the answers and pick cystic fibrosis!
• GASTROINTESTINAL SYMPTOMS: Pancreatitis, cholelithiasis, neonatal cholestasis, meconium ileus, rectal prolapse, chronic diarrhea, malabsorption with steatorrhea, fat soluble vitamin deficiencies (A, K, E, D), hypoproteinemia.
  • PEARLS: Regarding the fat-soluble vitamin deficiencies, look for problems with proprioception, ataxia, vision, coagulation, hypocalcemia,
• ACID-BASE ISSUES: Hypochloremic metabolic alkalosis. So, a low chloride and high bicarbonate level.
• ELECTROLYTE ABNORMALITIES: Hyponatremia, Hypokalemia, Hypochloremia, Hypocalcemia. Sodium and chloride are lost in the sweat. Potassium can be lost in stool. Calcium can be low due to a vitamin D deficiency from fat malabsorption.
  • MNEMONIC: All of the electrolytes are low except for bicarbonate. This makes sense given the finding of hypochloremic metabolic alkalosis.
• ENDOCRINE SYMPTOMS: Diabetes mellitus, amenorrhea, failure to thrive
  • PEARLS:
    • Give VITAMIN A, D, E, and K supplementation.
    • If a child presents with rectal prolapse or meconium ileus/plug, screen for cystic fibrosis! For meconium ileus, the boards could mention a “ground glass” on abdominal X-ray.
    • Patients can have cystic fibrosis exacerbations in which they produce quite a bit of mucus, sputum, and have a difficult time breathing. Along with respiratory nebulizer treatments, treat with an aminoglycoside (possibly inhaled tobramycin) and an anti-pseudomonal –cillin drug, such as piperacillin.
    • PNEUMONIAS: Staphylococcus infections are more common early in life, followed by pseudomonas. Lifetime colonization is common with these two organisms as well as Haemophilus influenzae. The role of Streptococcus pneumoniae in cystic fibrosis children is debatable, but it is usually not a colonizer. If there is mention of a nodular pneumonia in a CF patient, choose Staph. If the boards mention lung abscesses, choose Pseudomonas.
    • HEMOPTYSIS: This is not a common occurrence in children. If it happens, think CYSTIC FIBROSIS. Hemoptysis can also be seen in children with congenital heart disease (CHD) and chest trauma.
    • NASAL POLYPS: 20–70% of cystic fibrosis patients eventually develop nasal polyps. In children, and on the pediatric boards, nasal polyps are very commonly associated with cystic fibrosis.
      PEARL: If you are given the history of an asthmatic patient with nasal polyps, don’t choose CF. Look instead for an answer related to a classic triad of nasal polyps + asthma + aspirin (or NSAID) hypersensitivity.
      PEARL: Nasal polyps are also associated with allergic rhinitis and sinusitis.