Micronutrient deficiencies — branching viva

Branch 1 — The two-year-old with pallor and pica

The consultant presents a two-year-old boy with pallor, tiredness and pica whose diet is heavy in cow's milk. [1]

Examiner probes:

1. What is the most likely diagnosis and what in the history points to it? Lead the candidate to iron-deficiency anaemia with the microcytic film, the excessive cow's milk displacing iron-rich solids and the pica. [1]
2. How do you confirm it and what is the role of the C-reactive protein? The candidate should describe a low ferritin, low transferrin saturation and raised transferrin, and explain that ferritin rises in inflammation so the C-reactive protein must be read alongside it. [1]
3. What is the treatment and the expected timeline? Oral elemental iron at around three milligrams per kilogram per day, continued for about three months after the haemoglobin normalises, with a reticulocyte rise within one to two weeks and haemoglobin normalisation within two to three months. [1]

Branch 2 — The ten-month-old with bowed legs

The consultant pivots to a ten-month-old, exclusively breastfed infant with frontal bossing, widened wrists and bowing of the legs. [5]

Examiner probes:

1. What is the diagnosis and what are the risk factors here? Nutritional rickets from vitamin D deficiency, in the dark-skinned, covered or exclusively breastfed infant who gets little sun. [5]
2. What biochemistry confirms it? A low or low-normal calcium, low phosphate, raised alkaline phosphatase, secondary hyperparathyroidism and a low 25-hydroxyvitamin D, with a wrist radiograph showing widened, cupped metaphyses. [6]
3. What is the treatment and the important safety point? Cholecalciferol in a loading regimen then maintenance, with adequate dietary calcium, because rapid osteoid mineralisation on replacement can deepen the hypocalcaemia and seize the infant. [6]
4. What is the prevention dose? Vitamin D four hundred international units a day for infants and six hundred for children and adolescents. [5]

Branch 3 — The breastfed infant of a vegan mother

The consultant now presents an eight-month-old, exclusively breastfed infant of a vegan mother with lethargy, hypotonia, a tremor and loss of sitting. [7]

Examiner probes:

1. What is the diagnosis and why is it urgent? Vitamin B12 deficiency in the breastfed infant of a vegan mother, urgent because the neurological injury is severe and may not fully reverse. [7]
2. How do you confirm it? A low or borderline serum B12 with a raised methylmalonic acid and homocysteine, and a macrocytic anaemia with hypersegmented neutrophils, though the haemoglobin may be normal when the neurological signs lead. [7]
3. What is the treatment? Parenteral hydroxocobalamin daily for the first weeks then regular maintenance, with the mother supplemented and counselled on a reliable B12 source. [7]

Branch 4 — The refugee child with night blindness and a rash

The consultant finishes with a three-year-old recently arrived refugee with night blindness, a dry rough conjunctiva with white foamy patches, a periorificial and acral dermatitis, chronic diarrhoea and stunting. [9]

Examiner probes:

1. What are the two deficiencies here and what are the signs? Vitamin A deficiency with night blindness, Bitot spots and conjunctival xerosis, and zinc deficiency with the acral dermatitis, chronic diarrhoea and stunting. [9]
2. What is the immediate risk and the treatment of the vitamin A deficiency? The risk is corneal ulceration and blindness, and the treatment is immediate high-dose vitamin A. [9]
3. What is the population-level prevention in a deficient region? WHO high-dose vitamin A supplementation every four to six months from six months to fifty-nine months, at one hundred thousand international units for infants six to eleven months and two hundred thousand for children twelve to fifty-nine months, alongside dietary diversification. [11]
4. How do the mechanisms of deficiency converge across these children? Inadequate intake, malabsorption, increased losses and the increased needs of growth, each of which applies to one or more of the four cases. [11]

Closing synthesis

The consultant asks the candidate to summarise the principles that unify the four cases: recognise the deficiency by the system it serves, confirm with targeted biochemistry, replace the missing nutrient while treating the cause, and prevent with supplementation, fortification and dietary diversification, with early recognition the whole game because the developing brain and eye may not fully recover. [1] [7]