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Author Topic: The ABCs of XLH  (Read 4437 times)


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The ABCs of XLH
« on: December 17, 2017, 05:44:07 PM »
A glossary of terms of relevance to the XLH Community.

A is for Arthritis
Arthritis refers to inflammation, pain and stiffness in joints. It is often associated with aging, but in XLHers it tends to occur earlier than in the general population, and is worsened by the way bowed bones are misaligned when they meet at joints, especially in the feet, legs and hips. For information on managing and coping with arthritis, check out the Arthritis Foundation here: http://www.arthritis.org/

B is for Balance
B is for Balance: Current treatment of XLH requires a careful balance of phosphorus supplements with a proportionate amount of calcitriol. When the treatment is unbalanced, it can lead to hyperparathyroidism and kidney calcification. When properly administered, current treatment may reduce dental abscesses but does not appear to reduce enthesopathy (calcification of ligaments and tendons). You can read the journal article here: https://www.ncbi.nlm.nih.gov/pubmed/26176801

C is for Clinician's Guide to XLH
The Clinician's Guide to X-linked Hypophosphatemia is a comprehensive overview of XLH diagnosis, treatment (prior to burosumab) and prognosis, intended for healthcare providers, but of interest to patients who wish to be well-informed. You can download it here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3157040/

D is for Dental Abscess
A dental abscess is an infection that begins in the tooth. In XLHers, the abscess may occur spontaneously, and is caused by defects in the tooth structure, not due to poor dental hygiene. To help your dentist understand the unique challenges of XLH teeth, see our brochure for dental professionals: http://xlhnetwork.org/files/2015/0362/1533/DentalProBrochure_082417.pdf

E is for Endocrinology
Endocrinology is the medical specialty that focuses on the endocrine system (the glands that secrete hormones). In the U.S., it is the most common specialty for treating XLH, although nephrologists and rheumatologists may also have the right expertise. The Network maintains a database of health care providers with XLH experience. Contact us at info@XLHNetwork.org to find out if there's a doctor near you.

F is for Fibroblast Growth Factor 23
Fibroblast Growth Factor 23 (FGF23) is a hormone secreted by bone cells known as osteocytes. XLHers' bones secrete excessive levels of FGF23, which then lead to the wasting of phosphorus. Research into future treatment is focused on suppressing the FGF23, rather than replacing the wasted phosphorus. For an overview of how FGF23 is involved in XLH as well a number of other disorders, check out http://jasn.asnjournals.org/content/16/9/2565

Genetic transmission refers to how a gene is passed on. XLH is an X-linked (the relevant gene is on the X chromosome), dominant condition. (In some extremely rare variations, the gene may be located on other chromosomes and may be either dominant or recessive.) For the X-linked patient: An XLH father will always pass the affected gene to his daughters and never pass the affected gene to his sons. An XLH mother will, with each pregnancy, have a 50% chance of passing the affected gene to either sons or daughters. For more details (click on the links for great graphics that make it easier to understand): https://ghr.nlm.nih.gov/primer/inheritance/inheritancepatterns

H is for Hearing. Based on anecdotal evidence, there appears to be a link between XLH and hearing issues (hearing loss or tinnitus, also known as ringing in the ears). Unfortunately, there's no data yet to confirm that connection, and no consensus on the cause other than a recognition that hearing depends on the bones in the ears, and XLH affects bone quality. We hope to gather more data with our Natural History Study, which may then lead to more research into the cause of the hearing issues.

I is for ICD-10 codes. They are diagnostic codes used in the health care industry. They vary somewhat in their uses and even in their numbering from country to country. In the United States, getting the code right is critical for, among other things, determining whether a particular treatment or drug choice is appropriate and therefore covered by an insurance policy. The U.S. ICD-10 code for XLH (and the related genetic hypophosphatemias, but not for Tumor Induced Osteomalacia) is E83.31 ("familial hypophosphatemia"). Having the right code in your medical recormay be particularly important when there is an approved treatment for XLH, and you are working to convince your insurance company to cover the cost.

J is for joint damage. It is a common symptom of XLH, not just in the lower body where leg bones meet other leg bones, hips and ankles, but also in the upper body (arms and shoulders) and small joints (fingers and toes). Since your joints are predisposed to problems, it's even more important to do what you can to protect those joints. Some general suggestions can be found here: https://www.arthritis.org/living-with-arthritis/pain-management/joint-protection/joint-health.php And some exercises recommended for XLH joints generally (but check with your doctor) can be viewed at our Youtube channel here:  https://www.youtube.com/channel/UCOCxS6CV6NeNxoFFivOyNpg

K is for kidneys. The kidneys are where the phosphate-wasting of XLH occurs. The kidneys are not themselves defective, and a kidney transplant does not cure XLH. The kidneys are simply acting on an erroneous message from the endocrine system (the excessive levels of FGF23 triggers the phosphate-wasting). There's a good graphic on the interactions of FGF23 with the kidneys and the parathyroid glands here: http://www.kidney-international.com/cms/attachment/2043431466/2056030747/gr2.jpg

L is for listening. Listening is an important skill for health care providers. If your doctor won't listen to you, it's worth looking for other options. A health care provider who won't listen to reasonable concerns on little things isn't likely to listen when there are bigger issues, and that can be dangerous. (And make sure you're listening too!) If your health care provider isn't listening to you, and you're looking for a new provider, we may be able to help. The Network maintains a database of health care providers with XLH experience. Contact us at info@XLHNetwork.org to find out if there's an experienced doctor near you.

M is for misdiagnosis. The common misdiagnoses for XLHers include ankylosing spondylitis, fibromyalgia, DISH, rheumatoid arthritis, hypochondria, drug addiction. Note however that unfortunately having XLH does not preclude having additional diagnoses, so it is possible to have other serious conditions on top of the XLH. For reliable information on correct diagnoses for XLHers, check out The Clinician's Guide to X-Linked Hypophosphatemia here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3157040/

N is for natural history study. A natural history study collects data (survey responses, medical test results, etc.) to understand the progression of a disease from beginning to end. We'll be launching a natural history study of XLH later this year, and you can help by participating in the study. For more information on the value of natural history studies in rare diseases, check out this article from the FDA: https://events-support.com/Documents/Pariser.pdf

O is for osteomalacia. It refers to bone softness due to defective mineralization, comparable to rickets in children. Most adult XLHers have osteomalacia, which can lead to fractures, pseudofractures and pain. Osteomalacia is emphatically not the same as osteoporosis, and osteoporosis treatments (ie., bisphosphonates) are not a recognized treatment for the osteomalacia associated with XLH. There's also a phosphate-wasting disorder, Tumor Induced Osteomalacia, that has symptoms similar to XLH, including the bone softness, that's caused by a tumor instead of a genetic defect. You can read more about it here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3433741/

P is for Patient-focused Drug Development (PFDD) PFDD is a term used by the FDA, and it recognizes the fact that patients are the experts in the daily experience of a medical condition and in the treatment goals they're looking for. We'll be holding a PFDD meeting we're calling a Symposium on Hypophosphatemia: Past, Present and Future" on October 5, 2018 in Baltimore, MD, and we hope you'll be there to document your experiences with XLH.

Q is for quality of Life. We're fortunate that XLH is generally not life-threatening, reducing the quanity of life, but it can have significant impacts on the quality of life, due to pain, fatigue and mobility limitations. Little is known about the quality of life for adults with XLH, although we hope to learn more when our natural history launches. For now, you can read one study about the quality of life for rare bone disease patients (including XLH) here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5126812/

R is for rickets. Rickets is an often-misunderstood term, generally associated with lack of vitamin D and images of bowed legs. It actually refers to the softening (poor mineralization) of bones in children (it's called "osteomalacia" in adults), and it has a distinctive appearance in x-rays. There's even a scoring guide for reading x-rays and assigning the degree of rickets severity (designed for nutritional rickets, but also applicable to hypophosphatemic rickets) that you can read about here: https://www.ncbi.nlm.nih.gov/pubmed/10893912

S is for Standard of care. Standard of care, as defined by the National Cancer Insitute, is "Treatment that is accepted by medical experts as a proper treatment for a certain type of disease and that is widely used by healthcare professionals." https://www.cancer.gov/publications/dictionaries/cancer-terms/def/standard-of-care  Until recently, to the extent there was any standard of care for XLH and the related hypophosphatemias, it consisted of a complicated regimen of phosphate supplements and calcitriol, coupled with frequent monitoring of blood and urine samples, plus kidney scans. That may be changing now, with the expectation that burosumab will become the new standard of care, simpler for both patients and clinicians. We'll keep you updated when there is a consensus in the medical community on a new standard of care.

T is for treatment. The goal of XLH treatment is NOT to maximize the amount of phosphorus in the blood stream, but to make as much available to the system as possible without causing adverse effects in the parathyroids or kidneys. We've heard too many stories about patients who were given too much phosphorus either without any calcitriol or not enough calcitriol, leading to hyperparathyroidism or kidney calcificaction. To learn more about treatment (before burosumab), check out The Clinician's Guide to X-Linked Hypophosphatemia here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3157040/

U is for Ultragenyx. Ultragenyx Pharmaceutical is a "clinical-stage biopharmaceutical company committed to bringing to market novel products for the treatment of rare and ultra-rare diseases, with a focus on serious, debilitating genetic diseases." It was founded in 2010, and then in 2013 it entered into an agreement with the original creator of burosumab, Kyowa Hakko Kirin, to develop and commercialize the treatment in the Americas and the European Union. To read more about Ultragenyx, including press releases of data on burosumab (under the "investors" tab): http://www.ultragenyx.com/

V is for vitamin D. Vitamin D can refer to inactive vitamin D (generally vitamin D3, which can be purchased over-the-counter with other vitamins) or active vitamin D (calcitriol, which generally requires a prescriiption). Many XLHers have normal vitamin D3 levels in their blood, but have difficulty transforming it into the active vitamin D (calcitriol). Over-the-counter vitamin D3 (or the high-dose prescription cholecalciferol) does not prevent the phosphate-wasting and rickets/osteomalacia of XLH. Of course, some XLHers, like anyone else, may also have a vitamin D deficiency if you don't get enough through your diet or sun exposure, in which case you may be interested in some basic information on getting enough regular vitamin D3: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

W is for whole-life, whole-body. It used to be believed that XLH was purely a pediatric disorder and purely a skeletal disorder. What current science tells us however is that XLH is a whole-life, whole-body disorder. The human body requires adequate phosphorus throughout life, not just while bones are growing. Phosphorus is necessary for muscle formation/function and energy production, as well as for healthy bones and teeth. To learn more about the role of phosphorus: http://lpi.oregonstate.edu/mic/minerals/phosphorus

X is for XLH! X-linked hypophosphatemia is the most common form of genetically caused hypophosphatemia, believed to affect approximately 1 in 20,000 births, for a total of around 15,000 patients in the United States and over 300,000 worldwide. The "X-linked" refers to the X chromosome, which is where the genetic mutation causing the condition is found, and "hypophosphatemia" means "low levels of phosphorus in the blood."

Y is for you! Don't ever forget that you're an important part of both the XLH community and your (or your loved one's) experience with XLH. We invite you to attend the Symposium on Hypophosphatemia: Past, Present and Future on October 5, 2018 in Baltimore, Maryland, where you'll be able to share your experience as an adult with XLH or one of the related phosphate-wasting disorders. We're particularly interested in hearing from patients with the ultra-rare hypophosphatemias, like Tumor Induced Osteomalacia or autosomal hypophosphatemia, in order to get a diverse mix of experiences. If you'd like to be involved, please contact us at info@xlhnetwork.org

Z is for zest. One thing we've noticed in the majority of the XLHers we've met is that despite all of the challenges, most of you have an incredible zest for life. You can read about that zest for life in our book, Weak Bones, Strong Wills, the Stories of XLH, available at all the major online book distributors around the world, including Amazon: https://www.amazon.com/dp/1975845803/

And now you know the ABCs of XLH!

« Last Edit: February 24, 2018, 03:46:23 AM by GinJones »