MRCPCH Preparation Guide 2025: Everything You Need to Know

Explanation

Clinical reasoning

Key facts from the question

• Child: 3 years old, hypotonia, pale.
• CBC: Macrocytic anaemia → large red cells (↑ MCV).
• Mother: Vegetarian, anaemic during pregnancy.
• Neuro signs: Hypotonia suggests neurological involvement.

Linking the clues

• Macrocytic anaemia in a child → most common causes are Vitamin B12 or Folate (B9) deficiency.
• Neurological signs (hypotonia) → strongly point toward Vitamin B12 deficiency rather than folate, because folate deficiency does not cause neurological deficits.
• Maternal vegetarian diet → high risk of B12 deficiency (B12 is found mainly in animal products).
• Maternal deficiency during pregnancy → can cause low B12 stores in the infant, leading to symptoms in early childhood.

Why not the others?

• Iron profile → Iron deficiency causes microcytic anaemia, not macrocytic.
• Vitamin D → Related to bone health, not anaemia.
• Vitamin B9 (Folate) → Causes macrocytic anaemia but no neurological signs.
• Zinc → Deficiency causes growth delay, skin lesions, immune issues, not macrocytosis.

Best answer: a. Vitamin B12 level — to confirm deficiency and start treatment promptly.

*** Exam Pearl

Vitamin B12

Vitamin B12 is required for the formation of hematopoietic cells as well as maintaining cerebral and neurological functions. It is found in meat, fish, eggs, milk products and fortified cereals. Vitamin B12 is not found in fruit and vegetables and consequently those following a vegan diet and patients with malabsorption are at increased risk of deficiency. Prolonged deficiency of vitamin B12 will result in a megaloblastic anaemia and obvious lethargy and pallor. Other symptoms will include stomatitis and glossitis. If left untreated it can result in neurological and psychological changes including depression, confusion, numbness and visual changes.

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