Summary about Disease
Familial hypocalciuric hypercalcemia (FHH), also known as familial benign hypercalcemia, is a rare, lifelong genetic disorder characterized by mild hypercalcemia (elevated calcium levels in the blood) and inappropriately low calcium levels in the urine (hypocalciuria). It's usually benign, meaning it doesn't typically cause serious health problems. The body's calcium regulation is altered, but it's generally well-tolerated.
Symptoms
Most individuals with FHH are asymptomatic, meaning they have no noticeable symptoms. When symptoms do occur, they are typically mild and may include:
Fatigue
Weakness
Thirst
Frequent urination
Constipation
Muscle aches Rarely, more severe symptoms like pancreatitis may occur.
Causes
FHH is almost always caused by a genetic mutation. There are several types of FHH, with the most common being FHH type 1, caused by mutations in the CASR gene, which encodes the calcium-sensing receptor. This receptor is responsible for detecting calcium levels in the blood and regulating parathyroid hormone (PTH) secretion. Mutations in other genes such as *GNA11* and *AP2S1* can also cause FHH, resulting in FHH type 2 and FHH type 3 respectively. The condition is usually inherited in an autosomal dominant pattern. This means that only one copy of the mutated gene is needed for a person to be affected.
Medicine Used
4. Medicine used There's generally no medication specifically used to treat FHH. Because the hypercalcemia is usually mild and well-tolerated, treatment is generally unnecessary. In rare cases where symptoms are significant, medications to lower calcium levels may be considered, but these are not usually effective long-term. Parathyroidectomy (surgical removal of the parathyroid glands) is generally not recommended as it is usually ineffective in normalizing calcium levels in FHH.
Is Communicable
No, FHH is not communicable. It is a genetic condition, not an infectious disease. It cannot be spread from person to person.
Precautions
Since FHH is usually benign, specific precautions are generally not needed. However, it's important to:
Inform your healthcare provider about your diagnosis, especially before any medical procedures or if you develop any new symptoms.
Genetic counseling may be helpful if you are planning to have children.
Avoid unnecessary calcium supplementation, as this could worsen the hypercalcemia.
How long does an outbreak last?
FHH is not an "outbreak" type of disease. It is a chronic, lifelong condition. The hypercalcemia is present from birth or early childhood and typically persists throughout life.
How is it diagnosed?
Diagnosis typically involves:
Blood tests: To measure calcium, parathyroid hormone (PTH), and phosphate levels. FHH is characterized by mild hypercalcemia, normal to slightly elevated PTH, and low to normal phosphate.
Urine tests: To measure calcium excretion in the urine (24-hour urine collection). Low urinary calcium excretion (hypocalciuria) is a key diagnostic feature.
Calcium/creatinine clearance ratio: A calculation used to estimate urinary calcium excretion relative to kidney function. A ratio <0.01 is suggestive of FHH.
Family history: Assessing whether other family members have hypercalcemia.
Genetic testing: To confirm the diagnosis by identifying a mutation in one of the genes known to cause FHH (e.g., CASR, *GNA11*, *AP2S1*).
Timeline of Symptoms
9. Timeline of symptoms The hypercalcemia of FHH is typically present from birth or early childhood and persists throughout life. Symptoms, if present, can occur at any point but are usually mild. The timing of symptom onset is variable and unpredictable. Some individuals remain asymptomatic their entire lives.
Important Considerations
Distinguishing FHH from Primary Hyperparathyroidism (PHPT): It is very important to differentiate FHH from PHPT. PHPT requires surgical intervention.
Neonatal Severe Hyperparathyroidism (NSHPT): If both parents have FHH, there's a risk that their child could inherit two copies of the mutated gene, leading to NSHPT, a very severe form of hypercalcemia requiring urgent medical intervention (parathyroidectomy).
Genetic Counseling: Genetic counseling is highly recommended for individuals with FHH and their families.
Lack of effective treatment: Due to altered calcium set-point, routine treatments for hypercalcemia often fail in FHH.