This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Familial hypocalciuric hypercalcemia (FHH) type 3 is one of three recognized types of FHH, an inherited condition that causes abnormally high levels of calcium in the blood (hypercalcemia). FHH also causes high levels of parathyroid hormone (PTH) and low levels of calcium in the urine (hypocalciuria). In most cases, FHH does not cause signs or symptoms. However, some people with FHH do report symptoms. Signs and symptoms that may occur in some people with FHH type 3 include high magnesium in addition to calcium, general symptoms of hypercalcemia (such as weakness, fatigue, muscle pain, constipation, depression, confusion, and excessive thirst), lower bone mineral density, behavioral disorders, and learning disabilities. FHH type 3 is caused by a mutation in the AP2S1 gene and inheritance is autosomal dominant. Treatment is generally not necessary in people with no signs or symptoms of FHH. In severe cases however, removal of the parathyroid gland (parathyroidectomy) may be recommended.
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