RESUMEN
Hypocalcemia is due to Hypoparathyroidism, Vitamin D deficiency, Hypomagnesemia, Inadequate calcium intake. The benefits of breast-feeding are well established. There are no need to supply calcium or Vitamin D in breast-fed infant. We report a case of infantile hypocalcemia caused by Vitamin D deficiency in exclusively breast-fed infant. He had no hypocalcemic symptom and hypocalcemia was found incidentally by routine laboratory tests during pneumonia treatment. He was presented with a low serum calcium level and 1,25(OH)2 Vit D3 level and high PTH. He was improved by Calcium and Vitamin D supplement. After then his mother continued breast feeding exclusively and resisted to feed her baby weaning food. During follow up period, hypocalcemia was recheked after discontinuation of vitamin D supplement. At 11 months of age, the calcium level was normal without vitamin D supplement after he had eaten weaning food. This report describes a case of hypocalcemia induced by vitamin D deficiency in exclusively breast-fed infant, with review of the literature.