9th May 2025

A 4-month-old infant presents to ED with his parents due to increasing episodes where he cries until he looks blue and appears to take deep breaths.

A 4-month-old infant presents to ED with his parents due to increasing episodes where he cries until he looks blue and appears to take deep breaths. They have recently emigrated to the UK from India, where he was born via normal vaginal delivery at home. He has no known past medical history. Mum is fit and well but explains that she has type-1 diabetes.  

On examination, he looks cyanosed, and pulse oximetry shows reduced oxygen saturations when comparing pre- and post-ductal readings. He has a loud, harsh ejection systolic murmur heard at the left sternal edge.

Which of the following is the most likely underlying diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.