A hypocalcemic child with a novel activating mutation of the calcium-sensing receptor gene: successful treatment with recombinant human parathyroid hormone.
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Mittelman SD, Hendy GN, Fefferman RA, Canaff L, Mosesova I, Cole DE, Burkett L, Geffner ME
A hypocalcemic child with a novel activating mutation of the calcium-sensing receptor gene: successful treatment with recombinant human parathyroid hormone.
J Clin Endocrinol Metab. 2006 Jul;91(7):2474-9. Epub 2006 Apr 11.
- PubMed ID
- 16608894 [ View in PubMed]
- Abstract
CONTEXT: Persistent hypercalciuria, with the attendant risk of nephrocalcinosis and eventual renal failure, is common in hypoparathyroid patients, especially those with activating mutations of the calcium-sensing receptor (CASR) gene, being treated with oral calcium and calcitriol. Treatment with replacement PTH may be warranted, although this has yet to be evaluated in children. OBJECTIVES: The objectives of this study were to identify the cause of the disorder in a young hypocalcemic patient and to assess the efficacy of treatment of the patient with recombinant human PTH(1-34). SUBJECT: An infant presenting with hypocalcemia at 3 wk of age was studied. METHODS: CASR gene mutation analysis was performed on genomic DNA of the proband and family members. The patient was treated with twice-daily administration of recombinant human PTH(1-34) over a 17-month period. RESULTS: The proband was heterozygous for a de novo novel missense mutation (L727Q), on the border between transmembrane helix 4 and intracellular loop 2 of the CASR. When transiently expressed in a human embryonic kidney 293 cell line, the mutant receptor demonstrated a significant leftward shift in the extracellular calcium/intracellular signaling dose-response curve vs. that for the wild-type receptor [EC(50); mutant, 2.59 +/- 0.11 mm (mean +/- se) vs. wild-type, 3.78 +/- 0.12 mm, P < 0.001]. During treatment with PTH(1-34), the patient had no further serious hypocalcemic episodes, and his urinary calcium excretion declined remarkably. CONCLUSION: PTH should be evaluated further as a treatment of autosomal dominant hypocalcemia in young patients.