What symptom supports a diagnosis of cystic fibrosis in an infant?

In the context of cystic fibrosis, frothy stools are a significant symptom that supports the diagnosis, particularly in infants. This is due to the malabsorption of nutrients, which occurs as a result of pancreatic insufficiency—a hallmark of cystic fibrosis. The thick, sticky mucus characteristic of this condition can obstruct the pancreatic ducts, preventing digestive enzymes from reaching the intestines. As a result, infants with cystic fibrosis often produce stools that are bulky, greasy, and frothy, accompanied by an unpleasant odor, indicating inadequate fat absorption.

While yellowing skin could indicate conditions such as jaundice, frequent cough might suggest various respiratory infections or conditions, and tachycardia could be indicative of multiple health issues, frothy stools provide a more direct link to the digestive and pancreatic abnormalities associated with cystic fibrosis. Thus, the presence of frothy stools is a compelling indicator that warrants a further evaluation for cystic fibrosis in an infant.