Secondary immunodeficiency — formative SAQs

SAQ 1 (10)

A seven-year-old boy with acute lymphoblastic leukaemia, day twelve of induction chemotherapy, presents with fever of 39 °C. His absolute neutrophil count is 0.2 × 10⁹ per litre. He looks flushed and tachycardic but is normotensive. [1] [4]

a) Define secondary immunodeficiency and state why this child is immunodeficient. (2 marks) [1]

b) Outline your immediate management, including the timing of key interventions. (3 marks) [1] [4]

c) Explain how the cause predicts the infecting organism, giving the predicted organism class for chemotherapy-induced neutropenia. (2 marks) [1]

d) Describe the prophylaxis and vaccination principles that belong in his long-term plan as he proceeds through treatment. (3 marks) [4] [1]

SAQ 2 (10)

A four-year-old girl who underwent splenectomy for hereditary spherocytosis is brought in with a six-hour history of high fever and rigors. She is fully vaccinated for her age but has been inconsistent with prophylaxis. [5] [1]

a) What is the immediate threat, and what emergency management is required? (3 marks) [5] [1]

b) Explain the mechanism by which asplenia disables immunity and the organisms it predicts. (2 marks) [5]

c) Outline the long-term prevention plan: prophylaxis, vaccination, and the family's sick-day action plan. (3 marks) [5] [1]

d) State two other secondary causes of immunodeficiency that, unlike asplenia, may be reversible when the cause is treated, and name the mechanism in each. (2 marks) [1] [3]