title: Anticonvulsant treatment associated with intractable hypocalcaemia in a female child with hypoparathyroidism.
abstract: BACKGROUND
  We report the case of a female infant with hypoparathyroidism due to an activating mutation in the calcium-sensing receptor gene.
  
  
  METHODS
  The child presented in the neonatal period with clinical seizures associated with severe hypocalcaemia, hyperphosphataemia, low parathyroid hormone levels and elevated urine calcium:creatinine ratios. She required intravenous calcium and phenobarbitone initially, and then oral 1-alfacalcidol (1-AC) and phenobarbitone were started. The patient had intractable hypocalcaemia in the first 5 months of life despite escalating doses of 1-AC. When the phenobarbitone was stopped at 5 months of age she was admitted soon after with symptomatic hypercalcaemia. We postulate that the phenobarbitone increased the metabolism of 1-AC and thus she needed large doses of 1-AC to treat hypocalcaemia until the phenobarbitone was stopped. Her parents had no biochemical abnormalities on testing.
  
  
  RESULTS
  Molecular genetic analysis confirmed that our patient had a de novo missense variant, c.682G>A (p.Glu228Lys) in exon 4 of the calcium-sensing receptor.
  
  
  CONCLUSIONS
  This case report highlights the importance that clinicians caring for children on vitamin D and its analogues are aware of the interaction with phenobarbitone, which can result in symptomatic hypocalcaemia. 1-AC should be stored at 2-8°C, otherwise it will be rendered inactive.
authors.affiliation: Department of Paediatrics, Mater Dei Hospital, Msida, Malta.
authors.forename: Nancy
authors.initials: N
authors.lastname: Formosa
authors.forename: John
authors.initials: J
authors.lastname: Torpiano
authors.forename: Jeremy
authors.initials: J
authors.lastname: Allgrove
authors.forename: Mehul T
authors.initials: MT
authors.lastname: Dattani
mesh_terms: D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D004347:Drug Interactions; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000009:adverse effects* / Q000627:therapeutic use; D006934:Hypercalcemia / Q000139:chemically induced*; D006996:Hypocalcemia / Q000150:complications* / Q000188:drug therapy / Q000235:genetics; D007011:Hypoparathyroidism / Q000150:complications* / Q000235:genetics; D007223:Infant; D010634:Phenobarbital / Q000009:adverse effects* / Q000627:therapeutic use; D012640:Seizures / Q000150:complications* / Q000188:drug therapy / Q000235:genetics; D016896:Treatment Outcome
chemical_list: D000927:Anticonvulsants; D006887:Hydroxycholecalciferols; C008088:alfacalcidol; D010634:Phenobarbital