Familial hypophosphatemia

Familial hypophosphatemia, in its X-linked form, is an inherited disorder of phosphate balance in which PHEX gene variants raise fibroblast growth factor 23, so blood phosphate falls and bones and teeth develop poorly. It is rare, follows an X-linked pattern and affects both sexes, since females with one altered gene usually have similar features. The excess hormone reduces phosphate absorption from the intestine and its reabsorption by the kidneys. Severity varies widely: some people have low phosphate alone, while others show slow growth, bowed legs, bone pain, rickets in childhood, osteomalacia with stress fractures in adults, dental abscesses and hearing loss. Treatment combines vitamin D and phosphate supplements with a newer medicine that counters the surplus hormone. Starting treatment early is favoured, and corrective surgery may be needed for established deformities.

Seek urgent care for very high thirst and urination with vomiting or drowsiness, or for severe weakness with a very slow or fast pulse. See a doctor for unexplained weight change, constant tiredness, feeling unusually hot or cold, or a family history of diabetes or thyroid disease. Call the local emergency number for any symptom that is sudden and severe. This page is a reference for healthcare professionals and does not replace an assessment.