Hypercalcemia, familial benign type 2

Hypercalcemia, Familial Benign Type 2 (FBH2) is a rare genetic disorder characterized by mildly elevated serum calcium levels with minimal or no symptoms. It is an autosomal dominant condition, meaning that it can be passed down from one generation to the next when only one parent carries the mutated gene responsible for the disorder. FBH2 is one of the types of hypercalcemia, specifically categorized under familial benign hypercalcemia (FBH) or familial hypocalciuric hypercalcemia (FHH), which includes several subtypes.

Etiology and Genetics

FBH2 is caused by mutations in the GNA11 gene, which encodes a protein involved in the regulation of calcium levels in the body. This gene plays a crucial role in the signaling pathways that control calcium sensing within the parathyroid glands and the kidneys. Mutations in GNA11 disrupt normal calcium sensing, leading to inappropriate suppression of parathyroid hormone (PTH) secretion and reduced renal calcium excretion, which in turn results in elevated serum calcium levels.

Clinical Presentation

Individuals with FBH2 typically exhibit mild to moderate hypercalcemia. Unlike more severe forms of hypercalcemia, FBH2 usually presents with few, if any, symptoms. When symptoms do occur, they may include nonspecific manifestations such as fatigue, mild abdominal pain, or increased urination. Due to the benign nature of the condition, it is often discovered incidentally during routine blood tests.

Diagnosis

The diagnosis of FBH2 is based on clinical findings, family history, and genetic testing. Key diagnostic criteria include mild to moderate hypercalcemia, inappropriately normal or elevated PTH levels, and low urinary calcium excretion. Genetic testing can confirm the presence of a mutation in the GNA11 gene, providing a definitive diagnosis.

Management and Treatment

Management of FBH2 focuses on monitoring calcium levels and maintaining a normal lifestyle. In most cases, no specific treatment is required. Patients are advised to stay hydrated and avoid medications or supplements that could exacerbate hypercalcemia. In rare cases where symptoms become bothersome or calcium levels rise significantly, medical intervention may be necessary.

Prognosis

The prognosis for individuals with FBH2 is generally excellent. The condition does not typically lead to significant health problems, and life expectancy is normal. However, it is important for affected individuals to undergo regular monitoring of their calcium levels and to be aware of the potential for passing the condition on to their offspring.

See Also

• Hypercalcemia
• Parathyroid hormone
• Genetic testing

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