Neonatal Presentation of Cystic Fibrosis
A term girl is born to first cousin parents whose first child died at 9 years of age from cystic fibrosis. At 36 hours of age she is feeding and has a soft non distended abdomen, and the newborn screen shows a markedly raised immunoreactive trypsinogen. Which is the most common initial neonatal presentation of cystic fibrosis?
- A.Meconium ileusCorrect
- B.Failure to thrive
- C.Chronic productive cough
- D.Rectal prolapse
Explanation
Meconium ileus is the classic and commonest neonatal presentation of cystic fibrosis, occurring in 15 to 20 percent of affected newborns, and conversely 80 to 90 percent of infants with meconium ileus have cystic fibrosis. Deficient CFTR chloride and water secretion into the intestinal lumen, combined with pancreatic enzyme deficiency in utero, produces thick tenacious meconium that impacts in the terminal ileum. The infant fails to pass meconium in the first 24 to 48 hours and develops bilious vomiting and abdominal distension; abdominal radiograph shows dilated loops with a soap bubble or ground glass appearance and few air fluid levels, and contrast enema demonstrates a microcolon. Uncomplicated cases can be relieved by a hyperosmolar gastrografin enema, whereas volvulus, atresia or perforation requires laparotomy. Failure to thrive from pancreatic exocrine insufficiency with steatorrhea is very common in cystic fibrosis but develops over weeks to months rather than in the newborn period. Chronic cough and recurrent chest infection with Staphylococcus aureus and later mucoid Pseudomonas aeruginosa typically appear during infancy and childhood, not at birth. Rectal prolapse is a recognised and suggestive presentation in toddlers with untreated malabsorption, but it is neither neonatal nor the most common presentation. Other early clues include prolonged neonatal jaundice with a conjugated pattern and hypochloremic hypokalemic metabolic alkalosis from salt loss.
Why each option
- A.
- Correct. Meconium ileus is the classic newborn presentation of cystic fibrosis, and most infants with meconium ileus turn out to have the disease.
- B.
- Failure to thrive from pancreatic insufficiency is very common but evolves over the first weeks to months rather than presenting in the neonatal period.
- C.
- Chronic cough and recurrent infection develop during infancy and later childhood as endobronchial disease progresses.
- D.
- Rectal prolapse is a suggestive presentation in untreated toddlers with malabsorption, not a neonatal manifestation.
Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024, Cystic Fibrosis
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