Earliest presenting feature of cystic fibrosis in neonate is:
**Core Concept**
Cystic fibrosis (CF) is a genetic disorder caused by mutations in the CFTR gene, leading to abnormal chloride secretion and altered mucociliary clearance. In neonates, the earliest clinical manifestations are often related to respiratory and gastrointestinal symptoms due to the accumulation of thick, sticky mucus.
**Why the Correct Answer is Right**
Meconium ileus, a bowel obstruction caused by impacted meconium in the distal ileum, is the earliest and most common presenting feature of cystic fibrosis in neonates. This condition occurs due to the thick, dehydrated meconium that fails to pass through the intestinal tract, leading to bowel obstruction. The presence of meconium ileus is a strong indicator of cystic fibrosis, especially in the absence of other risk factors.
**Why Each Wrong Option is Incorrect**
**Option A:** Diarrhea is not a typical presenting feature of cystic fibrosis in neonates, as the condition is characterized by thick, sticky mucus, not watery stools.
**Option B:** Failure to pass meconium within the first 48 hours of life is a common issue in newborns, but it is not specific to cystic fibrosis and can have multiple causes.
**Option C:** Respiratory symptoms such as cough or wheezing may develop later in infancy or childhood, but they are not the earliest presenting feature of cystic fibrosis.
**Clinical Pearl / High-Yield Fact**
Meconium ileus is a critical presentation of cystic fibrosis in neonates, and its recognition can lead to early diagnosis and treatment of this life-threatening condition.
**Correct Answer: C. Meconium ileus. Meconium ileus.**