Differential Diagnosis for a 3-month-old Infant in Shock
Single Most Likely Diagnosis
- Anomalous Left Coronary Artery from the Pulmonary Artery (ALCAPA): This condition is characterized by the left coronary artery arising from the pulmonary artery instead of the aortic root. The presentation of irritability, poor feeding, and weight loss, followed by shock, along with ECG changes (Q waves in lateral leads indicating myocardial infarction), is highly suggestive of ALCAPA. The most likely finding on echocardiogram would be the left coronary artery arising from the pulmonary artery, which is a direct consequence of this anomaly.
Other Likely Diagnoses
- Left Coronary Artery Atresia or Stenosis: This could lead to similar symptoms due to reduced blood flow to the left ventricle, potentially causing myocardial ischemia or infarction. Echocardiogram findings might include left coronary artery dilatation as a response to the obstruction.
- Kawasaki Disease: Although less common in infants as young as 3 months, Kawasaki disease can cause coronary artery abnormalities, including dilatation. However, the typical presentation includes fever, rash, conjunctivitis, and changes in the lips and oral cavity, which are not mentioned here.
Do Not Miss Diagnoses
- Coronary Artery Thrombosis or Embolism: These are rare but potentially catastrophic conditions that could present with acute myocardial infarction and shock. The echocardiogram might show dilatation of the affected coronary artery or signs of myocardial dysfunction.
- Myocarditis: Inflammation of the myocardium can lead to heart failure and shock. While the ECG and echocardiogram findings might not specifically point to coronary artery anomalies, myocarditis is a critical diagnosis not to miss due to its potential for treatment and impact on prognosis.
Rare Diagnoses
- Williams Syndrome: A genetic disorder that can include supravalvular aortic stenosis and coronary artery abnormalities. It's less likely given the acute presentation but could be considered in the differential for coronary artery issues.
- Familial Hypercholesterolemia: Extremely rare in infants, this condition can lead to premature coronary artery disease. However, it would be unusual to present so acutely and severely at such a young age without a significant family history.