Hypophosphataemic Rickets

Authored by Dr Colin Tidy, 20 Apr 2011

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Hypophosphataemic rickets is characterised by growth retardation, rickets or osteomalacia, hypophosphataemia, and renal defects in phosphate reabsorption and in vitamin D metabolism.[1] The X-linked form (X-linked dominant) is the most common with a defect in phosphate transport in the proximal tubule leading to persistent hypophosphataemia and high levels of phosphate in the urine. Much rarer autosomal dominant, recessive, and sporadic forms also occur.

  • Rare.
  • The degree of bone involvement is much less severe in heterozygous females. However, there is often a maternal as well as paternal family history of short stature.[2]
  • Slow growth rate in the first year of life.
  • Reluctance to weight-bear when beginning to stand or walk.
  • Late dentition, multiple dental abscesses.
  • Intellectual development is unaffected.
  • Widened joint spaces and flaring at the knees may become apparent in children by their first birthday, particularly in boys.
  • When a child begins to stand and walk, bowing of the weight-bearing long bones develops quickly.
  • Urinary loss of phosphate is increased because of decreased renal tubular reabsorption of phosphate.
  • Blood tests for serum calcium, phosphate, alkaline phosphatase and parathyroid hormone:
    • Serum calcium levels may be normal or slightly low.
    • Phosphate levels are low.
    • Alkaline phosphatase levels are increased.
    • Parathyroid hormone level is normal or slightly raised.
  • X-rays of the wrists, knees, ankles, and long bones: no pathognomonic signs distinguish hypophosphataemic rickets from any other aetiology.
  • Periodic renal ultrasound is important to monitor for development of nephrocalcinosis.
  • Monitoring the ratio of calcium to creatinine in the urine is also important (a urinary ratio of calcium to creatinine more than 0.25:1 requires reduction of the vitamin D dosage to avoid nephrocalcinosis).
  • Patients under treatment should be carefully monitored for evidence of hyperparathyroidism.
  • Calcitriol (1,25-dihydroxycholecalciferol) - standard vitamin D preparations are not effective.
  • In some poorly growing patients, long-term growth hormone therapy given with conventional treatment improves linear growth.[3]
  • Calcitriol reduces but does not eliminate the risk of hypercalcaemic episodes, which may be frequent with vitamin D treatment.[2]
  • Amiloride and hydrochlorothiazide are given to increase calcium reabsorption and reduce the risk of nephrocalcinosis.[2]
  • Phosphate replacement is required because of the large urinary phosphate loss.
  • Osteotomy may be necessary for children whose diagnosis was delayed or whose initial treatment was inadequate.
  • Skull deformity may require treatment for synostosis.
  • Dental abscesses often require dental treatment.
  • Short stature, which is disproportionate, resulting from deformity and growth retardation of lower extremities.
  • Acute hypercalcaemia may occur during treatment.
  • Nephrocalcinosis, which does not usually progress to renal failure.
  • Hypertension may occur as a result of persistent hyperparathyroidism.
  • X-linked hypophosphataemic rickets is frequently associated with short stature, even when treatment is provided for a long time.[3]
  • Apart from the short stature, the prognosis is usually good with a normal lifespan.

Further reading and references

  1. Hypophosphatemic Rickets, X-linked Dominant, XLHR; Online Mendelian Inheritance in Man (OMIM)

  2. Roth KS; Hypophosphatemic Rickets, eMedicine, Feb 2009

  3. Saggese G, Baroncelli GI; Hypophosphataemic rickets. Horm Res. 200053 Suppl 3:57-60.

I am in the midst of this deficiency trying to recover from the horrible symptoms that it can cause. I want to hear from people who have overcome this deficiency and how they did it. If there was...

taro93814
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