Hypophosphatemic Rickets Treatment & Management

Updated: May 01, 2017
  • Author: James CM Chan, MD; Chief Editor: Sasigarn A Bowden, MD  more...
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Treatment

Approach Considerations

Treatment of hypophosphatemic rickets can be safely administered on an outpatient basis, although serum calcium concentrations must be periodically and carefully monitored. Conscientious follow-up is essential. [26]

In children receiving treatment, periodic renal ultrasonography studies are important to monitor for the development of nephrocalcinosis. Originally thought to be a sequela of the disease, this complication is now recognized as an iatrogenic result of therapy. Monitoring the ratio of calcium to creatinine in the urine is also important. A ratio of more than 0.25:1 requires reduction of the vitamin D dosage to avoid nephrocalcinosis. Consult a nephrologist for help treating any patient with possible kidney involvement.

Surgical care

Osteotomy to realign extremely distorted leg curvatures may be necessary for children whose diagnosis was delayed or whose initial treatment was inadequate. Skull deformity may require treatment for synostosis. [11]  Spontaneous abscesses often require periodic dental procedures.

Activity

If a patient is able, no activity restrictions are needed. Affected individuals obviously should not engage in contact sports until rickets is completely healed.

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Pharmacologic Therapy

The usual vitamin D preparations are not useful for treatment in this disorder because they lack significant 1-alpha-hydroxylase activity. Original treatment protocols advocated vitamin D at levels of 25,000-50,000 U/d (at the lower limit of toxic dosage), which placed the patient in jeopardy of frequent hypercalcemic episodes. Calcitriol is now more widely available and substantially diminishes, but does not eliminate, this risk. Amiloride and hydrochlorothiazide are administered to enhance calcium reabsorption and to reduce the risk of nephrocalcinosis. [10]

Healing of the rachitic changes typically occurs within 6-8 weeks of instituting treatment. During this time, maintain the calcitriol within the recommended dosage to maintain serum calcium and phosphate levels within reference ranges. Monitor these levels weekly over the first 2-3 months of treatment. Urinary calcium and phosphate excretion monitoring also are important.

The patient's requirements for calcium deposition and vitamin D to expedite the healing process diminish as healing progresses; thus, the patient with hypophosphatemic rickets becomes highly susceptible to hypercalcemia during this phase. Consider reducing the calcitriol dosage at this time, guided by the weekly calcium and phosphorus measurements, until a reduced and stable dosage is reached. Clinical trials have begun using a monoclonal antibody, KRN23, to block the action of increased fibroblast growth factor (FGF) on renal tubular reabsorption of phosphate (TRP). The safety and efficacy of this new approach, especially in children, will require extensive further investigation. [27, 28]

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