Скачать или смотреть XLH Community Impact Survey: Overview and Results

Jill H. Simmons, MD, Endocrinologist at Vanderbilt University Medical Center in Nashville, Tennessee, provides an overview of the XLH Community Impact Survey and its results.

My name is Dr. Jill Simmons. I am a pediatric endocrinologist at Vanderbilt University Medical Center in Nashville, Tennessee. I am director of the Pediatric Metabolic Bone Disorders program here at Vanderbilt. I have been working in the field of rare metabolic bone disorders for about 20 years.

Certainly, as part of that, I work with patients with XLH, primarily in the pediatric age range, but also some young adults as we think about some of the transition burdens that we have. I provide clinical care, also participate in clinical research and clinical trials, as well as this particular patient survey that we're going to be discussing today.

XLH Overview
XLH is short, I should say, for X-linked hypophosphatemia, or what we will often call it in pediatrics is X-linked hypophosphatemic rickets, because in the patient population that I care for, often it causes some specific skeletal findings that manifest as rickets on X-ray.

It's a genetic disorder, it's considered a rare genetic disorder, probably occurring in somewhere around 1 in 20,000 to 1 in 50,000 patients in the world. It's caused by variants in a gene called the PHEX gene, which is short for Phosphate-Regulating Endopeptidase Homolog X-linked gene. I will call that PHEX from here on out.

That gene defect causes chronic inappropriate elevation of something called FGF23, which is the phosphate-regulating hormone, Fibroblast Growth Factor 23, which works to regulate phosphate metabolism, particularly in the renal tubules.

If you have too much FGF23, what essentially happens is the phosphate transporter in the renal tubule will essentially stay wide open so that what's coming in from a dietary standpoint from phosphorus intake essentially immediately is released in the urine, leading to low serum phosphate.

When you have low serum phosphate, that causes a variety of manifestations that we can get into as we continue to talk. But again, the primary problem is an elevated FGF23 that needs to be managed in order to keep the serum phosphorus levels normal.