InstalabHypophosphatemic Rickets Genetic Test
Should you take a HPP Genetic test?
This test is most useful if any of these apply to you.
22 Biomarkers Included
- ALPLA gene that contains the instructions for making an enzyme your body uses to build strong bones and teeth and to process vitamin B6.
- CLCN5A gene that gives instructions for building a small molecular gate inside kidney cells, which helps those cells pull useful proteins back from the urine before they are lost.
- CTNSA gene that holds the instructions for making cystinosin, a protein that pumps the amino acid cystine out of cellular waste compartments; harmful changes in both copies cause a storage disease that damages kidneys, eyes, and other organs.
- CYP27B1A gene that contains the instructions for making the enzyme that converts vitamin D into its active, working form inside your body.
- CYP2R1A gene that builds the liver enzyme responsible for turning the raw vitamin D from sunlight, food, and supplements into the form your blood test actually measures.
- DMP1A protein made by bone cells that helps build and harden bones and teeth, and helps the body keep phosphate in balance.
- ENPP1A gene that produces an enzyme which dampens insulin's signal inside cells, with a common variant that can raise the risk of insulin resistance and type 2 diabetes.
- FAHA genetic test that looks for changes in a gene needed to make a liver enzyme that finishes breaking down the protein building block tyrosine, with faulty copies causing a rare but serious inherited disease.
- FAM20CA gene that carries instructions for an enzyme responsible for adding chemical tags to many of the proteins your body releases, especially those that build bones and teeth.
- FGF23A set of inherited variants in the gene that codes for a hormone controlling how your body handles phosphate and vitamin D.
- FGFR1A gene that codes for a cell surface receptor which receives growth signals, helping control how cells grow, develop, and survive.
- GATMA gene that contains the instructions for making an enzyme your body uses to produce creatine, the molecule that helps your cells store and release quick bursts of energy.
- GNASA gene that provides instructions for a key cellular messenger that helps your body respond to many hormones, controlling things like bone growth, weight regulation, and how your glands work.
- KLA gene that provides the instructions for making the Klotho protein, a molecule that helps regulate aging, brain health, kidney function, and the risk of several age-related diseases.
- NDUFAF6A gene that helps build part of the energy-producing machinery inside every cell, with rare inherited changes causing severe childhood disease and common variants linked to higher Alzheimer's risk.
- OCRLA gene that provides the instructions for making an enzyme essential for normal kidney, eye, and brain cell function, where harmful changes cause a rare inherited disorder.
- PHEXA gene that provides instructions for making an enzyme in bone and tooth cells, which helps your body keep the right level of phosphate in the blood and build strong bones.
- SLC2A2A gene that carries the instructions for building a transporter protein that moves sugar in and out of cells in the liver, pancreas, kidneys, and intestines.
- SLC34A1A gene that provides instructions for building a tiny pump in your kidneys that reclaims phosphate from urine, helping keep your bones, kidneys, and mineral balance healthy.
- SLC34A3A gene that gives instructions for making a kidney protein that pulls phosphate back into the body, helping keep your bone and mineral balance stable.
- SLC9A3R1A gene that codes for a scaffolding protein in your cells, which helps organize how the body manages minerals like calcium and phosphate and how kidney and bone cells handle them.
- VDRA common variation in the gene that codes for the protein your cells use to respond to vitamin D, which can influence how strongly vitamin D works in your body.
About Hypophosphatemic Rickets Genetic Test
A child whose legs keep bowing despite plenty of milk and sunshine. An adult with deep bone pain and stress fractures that no scan fully explains. A blood test that quietly flags low phosphorus once, then gets ignored. Each of these can be the first signal of an inherited disorder that drains phosphate from bone and kidney for years before anyone connects the pattern.
This panel sequences 22 genes that, when broken, cause that drain. Knowing which gene is responsible changes everything. It separates conditions that respond to a targeted antibody from those that need active vitamin D, and from those where active vitamin D is actually dangerous. It also tells you who in your family is likely to carry the same variant and at what age intervention works best.
What This Panel Reveals
Low blood phosphorus paired with rickets is not one disease. It is at least five different mechanisms with the same outward picture. This panel sorts them apart.
FGF23-driven phosphate wasting
The largest group is conditions where the body produces too much of a hormone called fibroblast growth factor 23 (FGF23), which tells the kidneys to dump phosphate into urine. The PHEX gene is the single most common culprit, causing X-linked hypophosphatemia, with a prevalence estimated at roughly 1 in 20,000. The genes FGF23, DMP1, ENPP1, FAM20C, KL, and FGFR1 each cause variants of the same end picture through different upstream defects in how FGF23 is produced, degraded, or signaled.
Kidney transporter defects
A second group breaks the kidney's own phosphate reabsorption machinery. The transporters encoded by SLC34A1 and SLC34A3 pull phosphate from urine back into the blood. When they fail, FGF23 stays low or normal, but phosphate is still lost. Active vitamin D rises in compensation, which then drives calcium absorption to dangerous levels and seeds kidney stones.
Vitamin D activation failures
A third group disrupts the vitamin D pathway itself. CYP2R1 in the liver and CYP27B1 in the kidney activate vitamin D in two sequential steps. VDR encodes the receptor that lets cells respond to it. Loss of any of these three causes vitamin D-dependent rickets, where phosphate is low as a downstream effect of disrupted calcium and bone biology.
Generalized kidney tubule dysfunction
A fourth group damages the kidney tubule broadly, leaking phosphate alongside amino acids, sugar, and bicarbonate in a pattern called Fanconi syndrome. CLCN5 (Dent disease), OCRL (Lowe syndrome), CTNS (cystinosis), SLC2A2 (Fanconi-Bickel syndrome), FAH (tyrosinemia type 1), and SLC9A3R1 belong here. Hypophosphatemia is one piece of a wider tubule problem.
Mineralization and overlap mimics
Finally, ALPL causes hypophosphatasia, which looks like rickets clinically but moves bone chemistry in the opposite direction (low alkaline phosphatase rather than high). GNAS underlies fibrous dysplasia and McCune-Albright syndrome, which can flood the system with FGF23 from skeletal lesions. GATM and NDUFAF6 cover rarer mitochondrial and metabolic causes where phosphate wasting is part of a wider picture.
How to Read Your Results Together
Genetic results land in plain categories: pathogenic, likely pathogenic, uncertain, or negative. The clinical meaning depends on which gene is hit and what the rest of your blood and urine work shows. The combinations below cover most of the diagnoses this panel is built to find.
| Genetic finding | Biochemistry that fits | What it points to |
|---|---|---|
| Pathogenic PHEX or FGF23 variant | Low phosphorus, high or inappropriately normal FGF23 | FGF23-driven rickets. Burosumab eligible. |
| Pathogenic SLC34A3 (biallelic) variant | Low phosphorus, low FGF23, high active vitamin D, high urine calcium | Hereditary hypophosphatemic rickets with hypercalciuria. Phosphate alone, no calcitriol. |
| Pathogenic CYP27B1 or VDR variant | Low phosphorus, low active vitamin D, low calcium, high parathyroid hormone (PTH) | Vitamin D-dependent rickets. Calcitriol with calcium. |
| Pathogenic ALPL variant | Low phosphorus possible, low alkaline phosphatase (the opposite of typical rickets) | Hypophosphatasia. Standard rickets treatment worsens it. |
Two situations need extra care. A variant of uncertain significance is not a diagnosis, and treating one as if it were leads to wrong therapy. And a negative panel does not rule out a genetic cause: a small share of cases involve deep intronic changes, structural rearrangements, or genes not yet linked to the disease.
What to Do with Your Results
A pathogenic finding belongs in the hands of a metabolic bone disease specialist or pediatric endocrinologist. The gene determines the treatment. FGF23-driven forms now have a targeted antibody, burosumab, which in a phase 3 trial in children improved rickets severity, leg deformity, and mobility compared with conventional phosphate and calcitriol. Vitamin D-dependent rickets responds to calcitriol with calcium. The hypercalciuric form (SLC34A3) is treated with phosphate alone, because adding active vitamin D fuels kidney calcium overload. Hypophosphatasia has its own enzyme replacement therapy, asfotase alfa.
A pathogenic result also opens family testing. Most of these conditions are inherited in patterns that put siblings, parents, and children at predictable risk. Identifying carriers early lets treatment start before bone deformity sets in. Genetic counseling is the standard first step.
If the panel comes back negative and the clinical picture is still strongly genetic, options include sending the data for periodic reinterpretation as variant databases grow, or moving to whole exome sequencing. Biochemical workup with serum phosphorus, calcium, alkaline phosphatase, PTH, FGF23, 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, and urine calcium and phosphate is the parallel track that anchors the diagnosis even before the gene is found.
When Results Can Be Misleading
Genetic tests do not measure your current biology. Someone on burosumab, calcitriol, or oral phosphate will still have whatever variants they were born with, and the panel will still find them. The reverse is also true: a negative panel does not mean your phosphorus is fine, only that the 22 genes screened are clean. The biochemical workup has to be read alongside the genetic one.
Variant classification also shifts over time. A finding called uncertain today may become pathogenic in two years as more families are reported. Ask the lab whether they offer reanalysis, and revisit borderline results periodically.