Hypophosphatemic Rickets Workup

  • Author: Karl S Roth, MD; Chief Editor: Stephen Kemp, MD, PhD   more...
 
Updated: Aug 23, 2011
 

Approach Considerations

Begin clinical laboratory evaluation of rickets with assessment of serum calcium, phosphate, and alkaline phosphatase levels. In hypophosphatemic rickets, calcium levels may be within or slightly below the reference range; alkaline phosphatase levels are significantly above the reference range.

Carefully evaluate serum phosphate levels in the first year of life, because the concentration reference range for infants (5.0-7.5 mg/dL) is high compared with that for adults (2.7-4.5 mg/dL). Hypophosphatemia can easily be missed in a baby.

Serum parathyroid hormone levels are within the reference range or slightly elevated, while calcitriol levels are low or within the lower reference range. Most importantly, urinary loss of phosphate is above the reference range.

Imaging studies

In all cases of rickets, the study of choice is radiography of the wrists, knees, ankles, and long bones. However, no pathognomonic sign on radiographs distinguishes hypophosphatemic rickets from any other etiology.

Next

Renal Tubular Phosphate Reabsorption

The renal tubular reabsorption of phosphate (TRP) is calculated with the following formula:

1 - [Phosphate Clearance (CPi) / Creatinine Clearance (Ccr)] X 100

The following formula calculates CPi:

[Urine Phosphate (mg/dL) X Volume (mL/min)] / Plasma Phosphate (mg/dL)

By substituting creatinine values for phosphate in the same formula, Ccr can also be calculated. A single early morning urine sample can be used, because CPi divided by Ccr causes units of urine volume to cancel each other.

The TRP in X-linked hypophosphatemia is 60%; normal TRP exceeds 90% at the same reduced plasma phosphate concentration.

Previous
Proceed to Treatment & Management
 
 
Contributor Information and Disclosures
Author

Karl S Roth, MD  Professor and Chair, Department of Pediatrics, Creighton University School of Medicine

Karl S Roth, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Nutrition, American Pediatric Society, American Society for Clinical Nutrition, American Society of Nephrology, Association of American Medical Colleges, Medical Society of Virginia, New York Academy of Sciences, Sigma Xi, Society for Pediatric Research, and Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Coauthor(s)

James CM Chan, MD  Professor of Pediatrics, Tufts University School of Medicine; Director of Research, The Barbara Bush Children's Hospital, Maine Medical Center

James CM Chan, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Pediatric Society, American Physiological Society, American Society of Nephrology, American Society of Pediatric Nephrology, and International Society of Nephrology

Disclosure: Nothing to disclose.

Specialty Editor Board

Arlan L Rosenbloom, MD  Adjunct Distinguished Service Professor Emeritus of Pediatrics, University of Florida College of Medicine; Fellow of the American Academy of Pediatrics; Fellow of the American College of Epidemiology

Arlan L Rosenbloom, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Epidemiology, American Pediatric Society, Endocrine Society, Florida Pediatric Society, Pediatric Endocrine Society, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London)  Professor and Chair, First Department of Pediatrics, Athens University Medical School, Aghia Sophia Children's Hospital, Greece; UNESCO Chair on Adolescent Health Care, University of Athens, Greece

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) is a member of the following medical societies: American Academy of Pediatrics, American College of Endocrinology, American College of Physicians, American Pediatric Society, American Society for Clinical Investigation, Association of American Physicians, Endocrine Society, Pediatric Endocrine Society, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Chief Editor

Stephen Kemp, MD, PhD  Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas for Medical Sciences College of Medicine, Arkansas Children's Hospital

Stephen Kemp, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association of Clinical Endocrinologists, American Pediatric Society, Endocrine Society, Phi Beta Kappa, Southern Medical Association, and Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

References

  1. Roth KS, Ward RJ, Chan JCM, Sarafoglou K. Disorders of calcium, phosphate and bone metabolism. In: Sarafoglou K, Hoffmann GF, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. New York, NY: McGraw Hill; 2009:619-64.

  2. Prié D, Friedlander G. Genetic disorders of renal phosphate transport. N Engl J Med. Jun 24 2010;362(25):2399-409. [Medline].

  3. Ariceta G, Langman CB. Growth in X-linked hypophosphatemic rickets. Eur J Pediatr. Apr 2007;166(4):303-9. [Medline].

  4. Haffner D, Nissel R, Wuhl E, Mehls O. Effects of growth hormone treatment on body proportions and final height among small children with X-linked hypophosphatemic rickets. Pediatrics. Jun 2004;113(6):e593-6. [Medline].

  5. Sochett E, Doria AS, Henriques F, et al. Growth and metabolic control during puberty in girls with X-linked hypophosphataemic rickets. Horm Res. 2004;61(5):252-6. [Medline].

  6. Bastepe M, Jueppner H. Inherited hypophosphatemic disorders in children and the evolving mechanisms of phosphate regulation. Rev Endocr Metab Disord. Jun/2008;9:171-180.

  7. Baum M, Syal A, Quigley R, Seikaly M. Role of prostaglandins in the pathogenesis of X-linked hypophosphatemia. Pediatr Nephrol. Aug 2006;21(8):1067-74. [Medline].

  8. Jehan F, Gaucher C, Nguyen TM, et al. Vitamin D receptor genotype in hypophosphatemic rickets as a predictor of growth and response to treatment. J Clin Endocrinol Metab. Dec/2008;93:4672-4682.

  9. Cho HY, Lee BH, Kang JH, et al. A clinical and molecular genetic study of hypophosphatemic rickets in children. Pediatr Res. Aug 2005;58(2):329-33. [Medline].

  10. Bresler D, Bruder J, Mohnike K, et al. Serum MEPE-ASARM-peptides are elevated in X-linked rickets (HYP): implications for phosphaturia and rickets. J Endocrinol. Dec 2004;183(3):R1-9. [Medline].

  11. Segawa H, Kaneko I, Tomoe Y, et al. The roles of Na/Pi-II transporters in phosphate metabolism. Bone. Feb/2009;Epub:Epub.

  12. Beck-Nielsen SS, Brock-Jacobsen B, Gram J, et al. Incidence and prevalence of nutritional and hereditary rickets in southern Denmark. Eur J Endocrinol. Mar/2009;160:491-497.

  13. Verge CF, Lam A, Simpson JM, Cowell CT, Howard NJ, Silink M. Effects of therapy in X-linked hypophosphatemic rickets. N Engl J Med. Dec 26 1991;325(26):1843-8. [Medline].

  14. Alon US, Monzavi R, Lilien M, et al. Hypertension in hypophosphatemic rickets--role of secondary hyperparathyroidism. Pediatr Nephrol. Feb 2003;18(2):155-8. [Medline].

 
Previous
Next
 
 
 
 
All material on this website is protected by copyright, Copyright © 1994-2012 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.

DISCLAIMER: The content of this Website is not influenced by sponsors. The site is designed primarily for use by qualified physicians and other medical professionals. The information contained herein should NOT be used as a substitute for the advice of an appropriately qualified and licensed physician or other health care provider. The information provided here is for educational and informational purposes only. In no way should it be considered as offering medical advice. Please check with a physician if you suspect you are ill.