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Am Fam Physician. 2004;69(12):2766

to the editor: I read with interest the article, “A Practical Approach to Hypercalcemia,”1 in the May 1, 2003, issue of American Family Physician. In addition to the causes of hypercalcemia that were listed in the article, family physicians who take care of infants also may want to consider other etiologies (see accompanying table).2

I also would be interested to know whether the authors think that substituting a spot urine calcium/creatinine ratio for a 24-hour urine calcium level is acceptable for evaluation of these infants. Timed urine collections can be difficult, especially in children.

Williams syndrome
Autosomal recessive hypophosphatasia
Secondary hyperparathyroidism from maternal hypocalcemia
Blue diaper syndrome
Jansen metaphyseal chondrodysplasia
Subcutaneous fat necrosis
Dietary phosphate deficiency

in reply: In infants, hypercalcemia is a rare but serious condition which should be investigated and treated without delay. The most common causes are iatrogenic administration of calcium (generally intravenously) and idiopathic infantile hypercalcemia, of which Williams syndrome is the severe variant.1 Severe primary hyperparathyroidism and homozygous familial hypocalciuric hypercalcemia presenting in the neonatal period may require rapid surgical intervention. As with adults, if hypercalcemia is confirmed with an elevated ionized calcium level, the measurement of intact parathyroid hormone level is the pivotal step in evaluation of the causative disorder. Calculation of a calcium/creatinine ratio using a random spot urine specimen correlates well with total 24-hour urinary calcium excretion.2 In the diagnostic algorithm for hypercalcemia, the urinary calcium/creatinine ratio can be used as a convenient and accurate substitution for a timed urine collection in term and preterm infants.3

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This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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