KROK 2 Medicine

Practice session

A 9-month-old infant who is exclusively breastfed without vitamin D supplementation and has minimal outdoor sun exposure presents with irritability, delayed motor milestones (inability to sit without support), and excessive head sweating. Physical examination reveals softened cranial bones with a ping-pong ball sensation upon parietal pressure (craniotabes), an enlarged anterior fontanelle (measuring 4x4 cm), prominent frontal bossing, palpable enlargement of the costochondral junctions ('rachitic rosary'), and bilateral widening of the wrists. Which pattern of biochemical laboratory values is characteristic of active vitamin D-deficiency nutritional rickets?

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