FRCPath Haem Part 1 MCQs-Haemostasis 505

A 5-year-old boy is referred to the paediatric haematology clinic with a history of recurrent bacterial infections, including multiple episodes of pneumonia, skin abscesses and severe periodontal infections since infancy.

His parents report that he has unusually pale skin and silvery-grey hair. Over the last 3 weeks, he has developed persistent fever, progressive hepatosplenomegaly and generalised lymphadenopathy.

Investigation	Result
Haemoglobin	91 g/L
WBC	3.2 × 10⁹/L
Neutrophils	0.8 × 10⁹/L
Platelets	178 × 10⁹/L
Triglycerides	3.6 mmol/L
Bone marrow	Haemophagocytosis present

Peripheral blood film examination reveals neutrophils containing toxic granules that stain positively with myeloperoxidase.

Which of the following statements best explains the underlying pathophysiology and the haematological findings in this patient?

A. Defective NADPH oxidase activity

B. Defective lysosomal trafficking and abnormal lysosome-related organelle formation

C. Defective integrin expression causes impaired neutrophil adhesion and migration

D. Defective lysosomal acidification causes accumulation of partially degraded material in neutrophils and lymphocytes.

E. Defective microtubule polymerisation causes impaired platelet aggregation and dense granule deficiency.