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  • • Benign condition of chronic, nonprogressive hypercalcemia with mildly elevated intact parathyroid hormone

    • Family history of hypercalcemia, especially in children

    • Etiology is a defect in the gene coding for the calcium sensing receptor; autosomal dominant transmission

    • Essentially is an elevation in the calcium set point

    • Often discovered incidentally with screening laboratory studies

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Symptoms and Signs

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  • • Usually none

    • May have polyuria and polydipsia or thirst

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Laboratory Findings

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  • • High serum calcium

    • Normal or mildly elevated intact parathyroid hormone level

    • Low urinary calcium

    • Urinary calcium clearance to creatinine clearance ratio of < 0.01

    • Possibly high serum magnesium level

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Rule Out

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  • • Primary hyperparathyroidism

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  • • Complete history (including family) and physical exam

    • Direct genetic testing for calcium sensing receptor defect

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  • • None required

    • Operative neck exploration does not alleviate this condition (with the exception of total parathyroidectomy, and surgically induced permanent hypoparathyroidism)

    • Genetic counseling important; offspring homozygous for mutation have severe neonatal hyperparathyroidism, which is potentially lethal

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References

Pollak MR et al. Mutations in the human Ca-sensing receptor gene cause familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. Cell. 1993;75:1297.  [PubMed: 7916660]
Marx SJ et al. The hypocalciuric or benign variant of familial hypercalcemia: clinical and biochemical features in fifteen kindreds. Medicine. 1998;60:397.
Egbuna OI. Brown EM. Hypercalcaemic and hypocalcaemic conditions due to calcium-sensing receptor mutations. Best Practice & Research in Clinical Rheumatology 2008, 22(1):129-48.  [PubMed: 18328986]

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