Familial hypocalciuric hypercalcaemia (FHH) is a rare genetic disorder characterized by abnormally elevated levels of calcium in the blood (hypercalcaemia) and lower than normal amounts of calcium in the urine (hypocalciuria). This condition is typically inherited in an autosomal dominant pattern, meaning that a mutation in one copy of the relevant gene is sufficient to cause the disorder.
FHH is caused by genetic alterations in the calcium-sensing receptor (CaSR) gene, which is involved in regulating the levels of calcium in the body. These mutations result in a dysfunction of the CaSR protein, impairing its ability to effectively detect and respond to changes in blood calcium levels.
Symptoms of FHH are generally mild, and affected individuals may not experience any noticeable symptoms. However, some individuals may develop episodes of abdominal pain, frequent urination, fatigue, and bone abnormalities due to chronically high levels of calcium in the blood.
Diagnosis of FHH involves blood and urine tests to measure calcium and related hormones, as well as genetic testing to identify mutations in the CaSR gene. Differential diagnosis is important to distinguish FHH from other causes of hypercalcemia, such as primary hyperparathyroidism or malignancy.
Treatment for FHH is typically not necessary, as the condition is considered benign. Individuals with FHH are often advised to monitor their calcium levels regularly, maintain a healthy diet, and avoid excessive vitamin D and calcium supplementation, as this can further increase calcium levels. Genetic counseling is recommended for affected individuals and their families to understand the inheritance pattern and for advice on family planning.
