Idiopathic infantile hypercalcemia (IIH) is a rare disorder caused by CYP24A1 loss-of-function mutation, resulting in impaired degradation of 1,25-dihydroxyvitamin D3. Pamidronate, an intravenously administered bisphosphonate, which is a potent inhibitor of bone resorption, has been reported only once for treatment IIH. We present a case of a previously healthy 5-month-old boy with IIH, where calcemia peaked to 5 mmol/L. Treatment with methylprednisone and furosemide had only minor effects; therefore, 2 intravenous infusions of pamidronate (0.6 mg/kg per dose) corrected the serum calcium level to 2.95 mmol/L. Furthermore, CYP24A1 homozygous mutation p.R396W (c.1186c>t) was identified in this patient, confirming the clinical diagnosis of IIH. In conclusion, IIH has a favorable outcome once properly detected and appropriately treated. Pamidronate has a beneficial effect in those patients with IIH where glucocorticoids and furosemide fail to meet the expectations.  

Department of Pediatrics Charles University Prague Faculty of Medicine in Hradec Kralove Hradec Kralove Czech Republic