Respiratory manifestations of systemic disease — short-answer question

Part A — Recognition and mechanism (10 marks)

a) State the diagnosis and how you recognise it (3 marks)

This boy has acute chest syndrome, defined by a new pulmonary infiltrate on chest imaging together with fever and respiratory signs — here pleuritic chest pain, cough, and hypoxia. The classic and dangerous timing is that it has evolved on day two of admission for a painful crisis rather than being present at arrival, which is exactly when vigilance drops. It is the leading cause of death in sickle cell disease, so it is recognised early and treated presumptively rather than after the full picture completes. ^{[1] [2]}

b) Explain the underlying mechanism (4 marks)

Acute chest syndrome is a self-amplifying vicious cycle. A trigger such as infection, a fat embolus from infarcting bone marrow, or pain-driven hypoventilation lowers oxygen, low oxygen promotes sickling in the pulmonary vessels, sickling causes vaso-occlusion and further infarction, and the resulting inflammation and atelectasis worsen oxygenation, which drives yet more sickling. His painful crisis and splinting from chest pain feed directly into this loop. ^{[2] [1]}

c) State why prompt action matters (3 marks)

The syndrome can progress within hours from a stable child to respiratory failure, and it is the commonest reason for intensive care and the leading cause of death in this group. Because pneumonia and pulmonary infarction coexist with it and are managed together, over-treating is far safer than trying to exclude it, so early aggressive treatment is the correct response to even an incomplete picture. ^{[1] [2]}