Treatment – XLH UK

How is XLH treated as a child?

Treatment of hypophosphataemic rickets in childhood is best done by a specialist centre. It not only involves medical treatment but also may need input from occupational therapy, physiotherapy, orthopaedic surgeons and ideally all of these working together.

Medical treatment traditionally has involved giving phosphate supplements multiple times a day. This is to allow enough phosphate in the body for the bones to heal and mineralise. Because the underlying renal phosphate wasting is not addressed, the oral phosphate supplements do not maintain normal blood phosphate levels for very long. Phosphate supplements should not be taken with calcium containing products as this can cause the phosphate and calcium to precipitate and not be absorbed. Along side phosphate supplements, active vitamin D is also given. The high levels of the hormone FGF23 prevents 25 hydroxyvitamin D (25OHD) from being converted into the active form 1,25 OHD. So supplements of 1,alphacalcidol or calcitriol is given.

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Due to these medications careful monitoring of bloods and urine need to be undertaken every 4-6 months during growth.
A new medication which tackles the raised levels of FGF23 has recently been recommended by the National Institute for Health and Care Excellence (NICE) and is now routinely used in children. Burosumab is a monoclonal antibody to FGF23 (ie it neutralises this) and reduces some of the phosphate wasting therefore increasing the blood phosphate levels. No other medication is needed. This is given as a subcutaneous injection every two weeks. The results seem very promising so far and it also seems to help with growth in children.

How is XLH treated as an adult?

Treatment almost always should take place at major research centres because of the rare nature of this disorder, and we strongly suggest relying on specialists familiar with the condition and are experienced in treating and managing it. These are most often endocrinologists or nephrologists with an interest in metabolic bone disorders.

Medications used in treating adults with XLH – typically an active form of Vitamin D [such as Rocaltrol (Calcitriol) or ONE-ALPHA®] and phosphorus (such as PHOSPHATE-SANDOZ®) – should be prescribed very carefully and taken in association with regular monitoring of blood and urine chemistries, including ParaThyroid Hormone (PTH) levels and urine calcium levels. The focus should not be on how high the phosphorus level can increase, as might be appropriate for other causes of a low blood phosphorus level, because in XLH the more phosphate you take, the more you eliminate in the urine, and the higher the PTH may go…which you will want to avoid. The medication can result in a variety of important effects on the kidneys that specialists will want to keep under tight control.

Progress is often measured in years, rather than months, so this can be very frustrating for parents and children alike. And if it’s not effective, or diagnosis came very late, surgical or orthopaedic intervention may be required.