Galactosemia — a neonatal metabolic emergency where lactose from breast milk or formula causes liver failure, sepsis, and brain damage in the first days of life in untreated infants with GALT deficiency.
Whole genome sequencing identifies the complete GALT genotype — including compound heterozygous combinations that determine long-term outcome variability — providing the precise molecular diagnosis that newborn screening enzyme assays do not supply.
Galactosemia
Classic galactosemia is an autosomal recessive inborn error of galactose metabolism caused by pathogenic variants in GALT (galactose-1-phosphate uridylyltransferase) on chromosome 9p13.3. GALT encodes the enzyme that converts galactose-1-phosphate and UDP-glucose to UDP-galactose and glucose-1-phosphate. Complete GALT deficiency leads to galactose-1-phosphate accumulation, which is toxic to the liver, kidneys, brain, and gonads. Classic galactosemia affects approximately 1 in 40,000-60,000 newborns in populations of Northern European ancestry. Duarte galactosemia — caused by the N314D variant (Duarte 2 allele) in compound heterozygosity with a classic pathogenic allele — is more common (approximately 1 in 4,000) and produces only partial enzyme deficiency with generally benign clinical outcomes.
Classical galactosemia presents in the neonatal period as a life-threatening crisis: jaundice, hepatomegaly, hypoglycemia, coagulopathy, renal tubular dysfunction, and a particular susceptibility to E. coli neonatal sepsis develop within days of initiating milk feeding. Without immediate dietary galactose elimination (discontinuation of human milk and transition to soy-based or elemental formula), untreated infants develop liver failure, permanent brain damage, and death. Newborn screening by enzyme assay or total galactose measurement identifies most affected infants before symptom onset; prompt dietary management in the first week of life prevents the neonatal crisis.
Despite successful acute management, long-term outcomes in classic galactosemia are frequently impaired: speech and language difficulties, intellectual disability of variable degree, neuromotor problems, and primary ovarian insufficiency (POI) — affecting approximately 80% of affected females regardless of dietary management — represent a chronic disease burden that dietary restriction alone does not prevent. Genotype-phenotype correlations exist: homozygous p.Gln188Arg variants (the most common classic allele in Europeans) are associated with worse long-term neurodevelopmental outcomes compared to some compound heterozygous genotypes. This prognosis counseling requires precise GALT genotyping beyond the enzyme assay that newborn screening programs use.
Duarte galactosemia (GALT N314D in compound heterozygosity with a classic allele) produces only 25% residual enzyme activity. Current evidence supports that Duarte galactosemia does not require dietary restriction in most cases — but distinguishing Duarte from classic galactosemia requires molecular genotyping.
Newborn screening provides an enzyme activity result. It does not identify the specific GALT variants — and without the genotype, clinicians cannot distinguish classic from Duarte galactosemia or provide accurate long-term prognosis.
Enzyme screening does not tell you which GALT variants are present — and that matters for lifetime prognosis
Newborn screening programs for galactosemia measure total galactose or GALT enzyme activity; they report an enzyme result, not a genotype. Without molecular GALT genotyping, clinicians cannot distinguish classic galactosemia from Duarte galactosemia — which has profoundly different dietary and prognostic implications. Classic galactosemia requires lifelong galactose restriction; Duarte galactosemia generally does not require dietary restriction. Additionally, within classic galactosemia, the specific genotype — homozygous p.Gln188Arg vs. compound heterozygous with a milder allele — provides information relevant to long-term neurodevelopmental outcome and ovarian insufficiency risk that enzyme activity alone cannot supply. Whole genome sequencing provides the complete GALT genotype.
Female carriers of classic alleles face primary ovarian insufficiency risk that requires proactive monitoring
Primary ovarian insufficiency (POI) develops in approximately 80% of females with classic galactosemia despite optimal dietary management — a consistent and poorly understood complication of the condition. The mechanism appears to involve direct galactose toxicity to oocytes and follicular development during fetal and early postnatal life. Recognizing POI risk early — which requires appropriate counseling beginning in adolescence about fertility preservation options and hormone replacement therapy needs — depends on having the correct galactosemia diagnosis confirmed by molecular testing. Carrier females (heterozygotes) also have some evidence of slightly elevated POI risk, though much less pronounced than in affected females.
Your full DNA (not just a part of it)
Traditional genetic testing looks at narrow sets of genes, missing most parts of your genome. We sequence your full genome — every gene and every region between genes.
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Easy to read and with answers you and your doctor can act on. Not a file to interpret — 200+ clinical reports, organized by category.
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Your DNA does not change, but genome science is accelerating. Every month, new variant-disease associations are discovered. We validate these findings and update your reports automatically. Your test becomes more valuable every year.
The results doctors bring to their hardest cases.
Forty years of uncertainty. One test.
A patient had spent decades in the UK healthcare system without a diagnosis. Dante data, accepted by NHS clinical teams at Queen Elizabeth University Hospital Glasgow, identified Noonan Syndrome and a RUNX1 leukemia-associated variant that had gone undetected. After 40 years, they finally had an answer.
A complete read delivers a complete picture.
A patient came to Dante to investigate periodic paralysis. Reading the complete genome identified a concurrent hereditary cardiac finding — Brugada syndrome — that their doctor confirmed with an ECG. The result also explained a family member's unresolved cardiac history. One test. Every answer in it.
Sequenced in 2019. The data worked in 2021.
Jennifer sequenced her genome with Dante two years before her breast cancer diagnosis. When treatment began, Dante's pharmacogenomics data showed her prescribed chemotherapy would cause serious adverse effects. Her doctor selected an alternative — and she started effective treatment from day one.
Every genetic question deserves a complete answer.
Whether you are searching for answers today or protecting your health for tomorrow, a complete read of your entire genome is the only place to start.
It runs in your family. Now you can know if it runs in your genes.
Your genome contains inherited variants associated with medical conditions like cardiac, cancer, and neurological. We read all of them — with the clinical depth to give the result meaning.
Learn more →When traditional lab tests say you're fine. And you know you're not.
Standard diagnostic tests check for a pre-selected set of answers. We sequence your full DNA — including parts that no test was designed to check. If the answer is in your genome, we will help you find it.
Learn more →Your diagnosis may be right. Your treatment plan may be incomplete.
Your genes determine which treatments are most likely to work — and which are not. We give your doctor the tools and insights to inform your treatment plan.
Learn more →You want to know before something forces the question.
Some people don't wait for a diagnosis or a family history to act. Whole genome sequencing gives you the complete genetic picture now — so you and your doctor can make informed decisions before anything becomes urgent.
Learn more →You already took a DNA test. Here's what it couldn't tell you.
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Dante Genome Test helped specialists at a UK national acute hospital in the identification of Noonan Syndrome and a rare leukemia-associated genetic variant that had gone undetected. That result changed the medical care of the patient.
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Common questions about whole genome sequencing.
What is the difference between whole genome sequencing and a targeted genetic test?
Targeted genetic tests — including standard hereditary cancer panels — read a pre-defined list of known variants in a specific set of genes. They are designed to find what they already know to look for. Whole genome sequencing reads your entire genome: all 6 billion base pairs, every gene, every region between genes. A Mayo Clinic study published in JAMA Oncology found that standard testing guidelines missed more than half of patients with inherited cancer mutations. Genome Test does not have a fixed list.
What will I receive when my results are ready?
Your Dante Genome delivers 200+ physician-ready reports organized by clinical category — hereditary cancer, cardiac conditions, rare diseases, pharmacogenomics, carrier status, and more. Reports are delivered to your secure Genome Manager and are formatted for direct clinical use. Your genome data is permanently retained and re-analyzed automatically as science advances.
What happens if a clinically significant variant is found?
If a pathogenic or likely-pathogenic variant is identified, it will be clearly flagged in your physician-ready report with clinical context, published evidence, and recommended next steps. We recommend sharing any clinically significant finding with your physician or a genetic counselor, who can guide decisions about surveillance, risk reduction, or cascade testing for family members.
How is this different from a consumer DNA test like 23andMe or AncestryDNA?
Consumer DNA tests use genotyping chips that read less than 0.1% of your genome — a tiny pre-selected set of common variants. They are optimized for ancestry and population-level traits, not clinical genetic findings. The Dante Genome Test sequences 100% of your genome at 30X coverage, the same standard used in clinical diagnostic settings. The two tests are not comparable in scope, methodology, or clinical utility.
How long does it take to get results, and how are they delivered?
Your collection kit ships within 48 hours of ordering. Once your sample arrives at our CLIA-certified laboratory, sequencing and analysis takes 6–8 weeks. Results are delivered securely to your Genome Manager, where you can access your reports, share them with your physician, and receive automatic updates as new findings are validated against your genome.
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Ships within 48 hours · Results in 6–8 weeks
