**Question:** A two-month-old infant is brought to the hospital emergency with marked respiratory distress. On examination, the infant has cyanosis and bilateral crepitations. Heart rate is 180/min, respiratory rate 56/min and the liver span 7.5 cm. The child has had repeated episodes of fever, cough and respiratory distress since the time of birth. Cardiovascular examination reveals a grade III ejection systolic murmur in left parasternal area and the chest X-ray reveals cardiomegaly with a narrow base and plethoric lung fields. What is the most likely diagnosis?

A. Congenital heart disease
B. Congenital pneumonia
C. Congenital respiratory disease
D. Congenital liver disease

**Correct Answer:** **A. Congenital heart disease**

**Core Concept:** The described clinical scenario is indicative of a congenital heart defect that is causing pulmonary hypertension and right-to-left shunting, resulting in cyanosis, bilateral crepitations, fever, and respiratory distress. The murmur, cardiomegaly, and plethoric lung fields are additional signs of a cardiomegaly and pulmonary hypertension.

**Why the Correct Answer is Right:**

The correct diagnosis is Congenital heart disease (option A), as the clinical presentation, auscultatory findings, and imaging findings (chest X-ray) are consistent with this diagnosis. The murmur (grade III ejection systolic murmur in left parasternal area) is a significant clue to the presence of a congenital heart defect. Cardiomegaly indicates an enlarged heart, while plethoric lung fields suggest increased pulmonary blood flow. The combination of these findings, along with the presence of fever and respiratory distress, strongly suggests congenital heart disease.

**Why Other Options are Incorrect:**

Option B (Congenital pneumonia) is incorrect due to the absence of fever and the presence of cyanosis, bilateral crepitations, and auscultatory findings (grade III ejection systolic murmur and cardiomegaly). Congenital pneumonia typically presents with fever, unilateral auscultatory findings, and no cardiomegaly.

Option C (Congenital respiratory disease) is incorrect because the clinical presentation, auscultatory findings, and imaging findings (cardiomegaly and plethoric lung fields) are more consistent with congenital heart disease rather than congenital respiratory disease. Congenital respiratory diseases typically present with respiratory distress, cyanosis, and auscultatory findings of crackles, rales, or wheezes, not a grade III ejection systolic murmur and cardiomegaly.

Option D (Congenital liver disease) is incorrect due to the absence of hepatomegaly, jaundice, and the presence of cardiomegaly, fever, and respiratory distress. Congenital liver diseases often present with hepatomegaly, jaundice, and absence of fever and respiratory distress, while cardiomegaly is more consistent with congenital heart disease.

**Clinical Pearl:**

In infants, respiratory distress, fever, and auscultatory findings (grade III ejection systolic murmur, cardiome