Miliary tuberculosis with hypercalcaemia-induced nephrogenic diabetes insipidus in an infant

Miliary tuberculosis (TB) is a rare but severe manifestation in infancy. Hypercalcaemia, well documented in granulomatous diseases like TB and sarcoidosis in adults, is infrequently reported in children. Nephrogenic diabetes insipidus induced by hypercalcaemia is a known complication. A female infant with right-sided neck swelling for 1 month (fine-needle aspiration showed tubercular lymphadenitis), on four-drug anti-tubercular therapy (ATT), admitted with complaints of polyuria, polydipsia and progressive weight loss over the last 2 weeks. Her father was on ATT for pulmonary TB. Investigations revealed hypercalcaemia with suppressed parathyroid hormone, elevated 25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃, high urinary calcium-to-creatinine ratio and dilute polyuria. Despite adequate hydration and ATT, hypercalcaemia persisted, necessitating corticosteroids, furosemide and a single dose of intravenous zoledronic acid. The child improved significantly with this approach. Hypercalcaemia in paediatric TB, although rare, can be a life-threatening emergency. Prompt recognition and multimodal treatment are crucial steps in management of the condition.