Zinc deficiency from malabsorption and sodium deficiency related to CFTR dysfunction also can contribute to poor growth.3 Serum sodium may be normal despite depleted body sodium. A urine sodium to creatinine ratio can be measured. Cystic Fibrosis Foundation (CFF) guidelines emphasize sodium supplementation from infancy onward and with exercise. Zinc supplementation can be instituted empirically if a child is failing to thrive.
Due to fat malabsorption and dysregulation of fatty acid metabolism, patients with CF frequently have essential fatty acid deficiency (EFAD),6 which contributes to poor growth and can lead to immune system compromise, dermatitis, alopecia, and thrombocytopenia.
In young children, picky eating can lead to inadequate weight gain. Although often a behavioral issue, underlying pathology from eosinophilic or celiac disease can manifest as picky eating, so these should be considered. All patients and families should be screened for food insecurity.
Attainment of nutritional goals is important. If a child is failing to meet goals, early discussions around invasive interventions such as nasogastric, gastrostomy, gastrojejunal, or jejunal tubes should be undertaken, as families may need time to become comfortable with these ideas.
Sixty percent of newborns with CF are born with complete pancreatic insufficiency (PI), and another 25% develop it by age 1 year.7 A baseline fecal elastase should be obtained in the neonatal period to assess for pancreatic sufficiency. Patients can develop PI at any time without early symptoms to indicate change. Annual monitoring with fecal elastase is recommended. A decrease in fecal elastase precedes steatorrhea. Steatorrhea develops only after lipase output falls below 10%. Fecal elastase can be falsely positive in watery stool and in severe nutritional depletion. In the latter case, testing should be repeated once nutritional repletion is addressed.
Pancreatic enzyme replacement therapy is critical to nutrient absorption and growth. It is important to optimize the timing of enzymes when the child is actively eating or immediately after, not prior to meals. Schools may need additional information about proper medication timing.
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