In 1995 the gene associated with XLH was identified and is now called PHEX.  The PHEX protein is known to be an endopeptidase which is expressed on the surface of osteoblasts.   Its substrate(s), while not yet identified, has (have) been given the name `phosphatonin'.

The search for continued understanding of the central role played by the PHEX endopeptidase forms the basis for an exploding area of research aimed at elucidating the body's mechanisms for phosphate homeostasis. Thus, research on XLH is one of the very hottest areas, at the moment, in the field of bone metabolism, growth and development.

The principal focus of contemporary research, given expression of PHEX in a variety of vectors, as well as a soluble secreted form, plus the recent identification of two novel protein factors - MEPE (a tumour-secreted protein associated with oncogenic hypophosphatemic osteomalacia [OHO]), and FGF23 (the protein produced by the gene affected in Autosomal Dominant Hypophosphatemic Rickets [ADHR], which exhibits symptoms nearly identical to those in XLH) - is to determine which of several possible candidates is phosphatonin.

Whichever candidate or candidates actually turns out to be the bona fide phosphatonin, there will be some potentially very useful therapeutic agents which will require more consideration in the relevant animal model (the Hyp mouse), and soon thereafter would be expected to be trialed for human use. The field is moving very fast indeed.

More detailed articles on ths subject are available on the members web space.

The PHEX Locus Database contains a wealth of information relating to PHEX and their page on PHEX Recent Literature often contains references to the latest published research on that topic.

An excellent source of information on XLH research is the OMIM entry.

An XLH Abstract Collection is also available on this web site.

An infrequently updated but large abstract collection covering a wide range of XLH issues including Therapeutic Research, Teeth Problems, Disease Presentation and research on the Mouse Model is also available at the Larry's old website.

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.