Cystic fibrosis.

Apuntes

A 2-month-old male infant is brought to the clinic for evaluation of poor weight gain, frequent vomiting, and constipation. He was born at term via spontaneous vaginal delivery with no complications. Since birth, his parents report that he has had large, foul-smelling, greasy stools and often seems to struggle while breathing during feeds. Despite adequate breastfeeding, his weight is below the 5th percentile. On exam, he appears undernourished, with mild abdominal distension. Chest auscultation reveals bilateral crackles, and digital clubbing is noted. A sweat chloride test is ordered and reveals a concentration of 72 mEq/L (normal <40 mEq/L). Which of the following is the most likely diagnosis? Cystic fibrosis. This infant’s presentation of failure to thrive, greasy and bulky stools (steatorrhea), recurrent respiratory symptoms (crackles and clubbing), and a positive sweat chloride test (>60 mEq/L) is classic for cystic fibrosis (CF)(D), an autosomal recessive disorder caused by mutations in the CFTR gene leading to defective chloride channels. The result is thick, viscous secretions that obstruct exocrine ducts in multiple organs. In the pancreas, this leads to enzyme deficie...