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What is familial hypophosphatemia?
Familial hypophosphatemia is an uncommon genetic disease, which occurs as a result of a reduction in blood phosphate levels and changes in vitamin D metabolism in the kidneys. These clinical characteristics result in bone deformities such as osteomalacia, rickets, and bone plate defects.
What are its signs and symptoms?
This condition usually occurs in young people, around the age of 18 months, although variation is also seen. Symptoms may include:
In infants:
- Unusual frame of the head
- Premature skull fusion
In children:
- Advanced bow legs or knees bend inwards
- Short frame of the body compared to the age
- Pain experienced during any activity
In adults:
- Pain due to osteomalacia (weakening of bones)
- Increased risk of fracture
- Arthritis risk
- Accumulation of minerals in the tendons
What are its main causes?
Genetic mutation is the main reason behind this condition, which occurs as a result of defects in various genes. The genetic defects responsible for this condition are likely to be passed on in the family. Research has found that the PHEX gene is where the mutations occur most commonly. This gene regulates the transfer of phosphates in our body. Many of them are involved in the regulation of proteins that are responsible for reabsorption of phosphates. These genetic defects, in turn, will ultimately result in the hyperactivity of the proteins leading to abnormally low phosphate levels in the blood. Rarely, the condition may be acquired as a result of non-malignant tumours.
Other types include:
- Autosomal dominant type
- X-linked hypophosphatemia
- Autosomal recessive type
How is it diagnosed and treated?
The Diagnosis will include a thorough physical examination and a battery of laboratory tests. Blood tests are usually ordered to check vitamin D and phosphate levels. Parathyroid hormone levels and calcium will also be checked as their levels may be imbalanced. Bone deformities may be checked via X-ray, MRI, and positron emission tomography (PET) scans.
Treatment includes:
- Supplemental salts of phosphates
- Vitamin D (active form)
- Mostly monoclonal antibodies have been used for X-linked type of hypophosphatemia.
There are increased chances of side effects due to the concomitant use of vitamin D along with phosphates. It is important to check these mineral levels to prevent further complications. Supportive treatments are an essential aid in the management of this condition. It is of utmost importance that the family members are counselled about this condition so that proper care is taken.
