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Genetic and Rare Diseases Information Center (GARD)

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Familial hypocalciuric hypercalcemia


Other Names for this Disease
  • Familial benign hypercalcemia
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Overview



What is familial hypocalciuric hypercalcemia?

How is familial hypocalciuric hypercalcemia inherited?


What is familial hypocalciuric hypercalcemia?

Familial hypocalciuric hypercalcemia (FHH) is a benign, inherited condition that causes abnormally high levels of calcium in the blood (hypercalcemia). Affected individuals usually do not have any signs or symptoms of the condition, and hypercalcemia is often diagnosed incidentally.[1] In some individuals, weakness, fatigue, thought disturbance, and/or excessive thirst (polydipsia) have been reported.[2] FHH is usually caused by mutations in the CASR gene, although abnormalities in other, unidentified genes have been documented. It is inherited in an autosomal dominant manner.[1] Treatment is typically considered unnecessary because it is a benign condition. FHH can be difficult to distinguish from primary hyperparathyroidism, for which parathyroidectomy is typically performed; individuals with FHH are typically advised to avoid parathyroidectomy.[2]
Last updated: 9/23/2011

How is familial hypocalciuric hypercalcemia inherited?

Familial hypocalciuric hypercalcemia (FHH) is inherited in an autosomal dominant manner. Individuals have two copies of each gene (one inherited from each parent). For a condition with autosomal dominant inheritance, one mutated copy of the gene in each cell is sufficient to cause the condition. An affected individual may inherit the mutated copy of the gene from an affected parent, or the mutation may occur for the first time in the affected individual. An individual with FHH has a 50% (1 in 2) risk to pass on the mutation to each of his/her children.

Although most affected individuals have one mutated copy of the gene, it is possible for an affected individual to have a mutation in both copies of the causative gene. These individuals may have very little (or no) function in the mutated gene and have a more severe variation of the disease called neonatal severe primary hyperparathyroidism (NSHPT). Because two mutated copies of the gene cause NSHPT, this condition is inherited in an autosomal recessive manner. This condition may become evident within the first week of life and can be life-threatening; aggressive medical management is usually needed.[3] It is also technically possible for an individual to have two separate mutations in the same copy of the gene responsible for FHH.

For answers to specific questions about an individual's circumstances, a consultation with a genetics professional is recommended. Genetics pprofessionals can answer questions about the diagnosis, natural history, treatment, mode of inheritance, and genetic risks to other family members.
Last updated: 9/23/2011

References
  1. A. Lienhardt-Roussie. Other search option(s)Alphabetical list . Orphanet. June 2006; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=405. Accessed 9/22/2011.
  2. Varghese J, Rich T, Jimenez C. Benign Familial Hypocalciuric Hypercalcemia. Endocrine practice. March-April 2011; http://aace.metapress.com/content/f0r7q246g0h68761/fulltext.pdf. Accessed 9/23/2011.
  3. David Goltzman. Approach to Hypercalcemia. Endotext.org. July 1, 2008; http://www.endotext.org/parathyroid/parathyroid4/parathyroidframe4.htm. Accessed 9/23/2011.