ROCKVILLE, MARYLAND - Since the PHEX gene was identified in 1995, access to the genetic test for XLH has been mostly limited to patients who are part of specific research projects. The reasons for this have been primarily financial and practical, as the demand for a commercially available XLH genetic test is limited. A new company, however, called GeneDx, based in Rockville, Maryland, USA, specializes in genetic testing for rare inherited diseases. Although GeneDx is less than two years old, its directors Dr. Sherri Bale and Dr. John Compton (formerly at NIH and NIAMS) are well known within the genetic/medical community. The coordinators of the XLH Network contacted Dr. Bale at GeneDx just after Christmas 2001 to see if they were interested in offering a genetic test for XLH. GeneDx did some investigation and contacted two researchers/clinicians (who we recommended) with XLH experience.

GeneDx decided that they would offer genetic tests for XLH (OMIM: 307800) as well as two other inherited forms of rickets, ADHR (OMIM: 193100) and the recessive alpha hydroxylase deficiency (OMIM : 264700) . The specific tests they offer are linked on the GeneDX website. The genetic test is done with tissue derived from a painless swab of the inside cheek. A specialist/doctor can order the test, or a patient can contact GeneDx directly. Although the initial test is relatively expensive, GeneDx has been successful in assisting individuals in getting full or nearly full reimbursement from insurance companies for many of their other diagnostic tests and would expect similar insurance coverage for these new tests. Pre-authorization is always advisable from insurance, of course, before doing the test if you hope to be reimbursed. Prenatal testing (amniocentesis) is available as is testing for multiple family members at a reduced cost. Reports of results are released to the ordering physician or genetic counselor, rather than to the patient directly.

The availability of a genetic test for XLH brings new diagnostic options for patients, but also carries new responsibilities and potential pitfalls. We have been in contact with patient support networks within the Genetic Alliance in an attempt to understand these issues better, and although we have developed an increasing file of notes on these issues, we hope to continue to share more information as it becomes available. Initial feedback from members of other rare disease organizations has been uniformly positive regarding GeneDx and the sort of genetic testing that they do.

We would be grateful if members discussed the test, their hopes, feelings and concerns, in public on our F-HYPDRR mailing list well as checking the resource material available in the Members Webspace concerning genetic testing and its implications, as we have worked hard to be a responsible committee investigating these issues prior to announcing these matters publicly in F-HYPDRR. The telephone number and website contacts for GeneDx are available on our Members WebSpace.

Last modified Aug 8, 2007

XLH is also known as X-Linked Hypophosphatemia (sometimes also spelled as hypophosphataemia), X-Linked Hypophosphatemic Rickets, Familial Hypophosphatemia, Vitamin D-Resistant Rickets (VDRR) Rickets and even Genetic Rickets. Its notable characteristics are bowed legs, short stature, poor teeth formation causing spotaneous dental abscesses, and low blood phosphorus levels.

© 2002-2007, The XLH Network Inc.
The authors of this web site are not medical professionals, and this information does not substitute for medical care. Information on these pages is based on biomedical research, published in peer-reviewed journals, and international research conferences. Additionally, in some cases anecdotal information is provided by subscribers of the F-HYPDRR group, a mailing list for The XLH Network Inc. A complete web-site bibliography is available. Please read our full disclaimer.