16th February 2024

An 8-month-old child presents with several episodes of diarrhoea and pneumonia

An 8-month-old child presents with several episodes of diarrhoea and pneumonia. Closer examination reveals he has a high-arched palate, small jaw and low-set ears. He also has a soft mid-systolic murmur at the 2ⁿᵈ intercoastal space with fixed splitting of his 2ⁿᵈ heart sound. Blood tests showed lymphopenia and mild hypocalcaemia. Chest X-rays showed bilateral infiltrates in keeping with pneumonia and an absent thymic shadow.

What is the likely underlying diagnosis?

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