What is Imerslund-Gräsbeck syndrome?
Imerslund-Gräsbeck syndrome (IGS), also known as megaloblastic anemia 1 or juvenile selective vitamin B12 malabsorption, is a rare inherited condition that prevents the body from properly absorbing vitamin B12 (cobalamin) from food in the intestines. Vitamin B12 is essential for making healthy red blood cells and keeping the nervous system working properly. Without enough B12, the body produces abnormally large, poorly functioning red blood cells — a condition called megaloblastic anemia — which leads to tiredness, weakness, and pale skin. Many children with IGS also have a kidney problem called proteinuria, where protein leaks into the urine, though this usually does not cause serious kidney damage. Symptoms typically appear in early childhood, often between 1 and 5 years of age, when the body's stored B12 runs out. Children may seem unusually tired, grow more slowly than expected, and may develop neurological problems if the condition is not treated promptly. The good news is that IGS responds very well to treatment with regular vitamin B12 injections, which bypass the absorption problem entirely. With lifelong B12 injections, most people with IGS can live healthy, normal lives. Early diagnosis and consistent treatment are key to preventing lasting nerve damage.
Key symptoms:
Extreme tiredness and low energy (fatigue)Pale or yellowish skinWeakness and poor muscle toneSlow growth or failure to thrive in young childrenLoss of appetiteIrritability or behavioral changesNumbness or tingling in hands and feetDifficulty walking or balance problemsDelayed development or regression of milestonesProtein in the urine (proteinuria), usually without obvious symptomsEnlarged liver or spleen in some casesRecurrent infections due to weakened immune function
Clinical phenotype terms (30)— hover any for plain English
- Decreased circulating vitamin B12 concentrationHP:0100502
- Malabsorption of Vitamin B12HP:0200118
- Abnormal blood 5-methyltetrahydrofolate levelHP:0410216
- Megaloblastic anemiaHP:0001889
- Macrocytic anemiaHP:0001972
- Hypersegmentation of neutrophil nucleiHP:0004821
- AnisopoikilocytosisHP:0004823
- Inheritance
- Autosomal recessive
- Passed on when both parents carry the same gene change; often skips generations
- Age of Onset
- Infantile
- Begins in infancy, roughly 1 month to 2 years old
Treatments
Source: openFDA + DailyMed · NDA / BLA labels with structured indications · refreshed weekly
No FDA-approved treatments are currently listed for Imerslund-Gräsbeck syndrome.
View clinical trials →Clinical Trials
View all trials with filters →Source: ClinicalTrials.gov · synced daily · phases, status, and PI names normalized at ingest
No actively recruiting trials found for Imerslund-Gräsbeck syndrome at this time.
New trials open frequently. Follow this disease to get notified.
Specialists
View all specialists →Source: NPI Registry + PubMed · trial PI roles cross-referenced with ClinicalTrials.gov · ranked by match score (publications + PI activity + community signal)
No specialists are currently listed for Imerslund-Gräsbeck syndrome.
Treatment Centers
8 centersSource: NORD Rare Disease Centers + NIH Undiagnosed Diseases Network (UDN) · centers verified active within last 12 months
Children's Hospital Colorado Rare Disease Program ↗
Children's Hospital Colorado
📍 Aurora, CO
👤 Boston Children's Hospital Rare Disease Program
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDBoston Children's Hospital Rare Disease Program ↗
Boston Children's Hospital
📍 Boston, MA
👤 Boston Children's Hospital Rare Disease Program
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
🏨 Children'sAnn & Robert H. Lurie Children's Hospital Genetics ↗
Lurie Children's Hospital
📍 Chicago, IL
👤 Boston Children's Hospital Rare Disease Program
🏥 NORDCincinnati Children's Hospital Medical Center ↗
Cincinnati Children's
📍 Cincinnati, OH
👤 Boston Children's Hospital Rare Disease Program
🏨 Children'sNationwide Children's Hospital Rare Disease Center ↗
Nationwide Children's Hospital
📍 Columbus, OH
👤 Boston Children's Hospital Rare Disease Program
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
Travel Grants
No travel grants are currently matched to Imerslund-Gräsbeck syndrome.
Community
No community posts yet. Be the first to share your experience with Imerslund-Gräsbeck syndrome.
Start the conversation →Latest news about Imerslund-Gräsbeck syndrome
Source: PubMed + NIH RePORTER + openFDA + clinical-journal RSS · last 30 days · disease-tagged at ingest by AI extraction with human QC
No recent news articles for Imerslund-Gräsbeck syndrome.
Follow this condition to be notified when news becomes available.
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How often does my child need B12 injections, and will this change over time?,How will we know if the treatment is working — what tests should we do and how often?,Should my other children be tested for this condition?,What are the signs that my child's B12 levels are dropping and I should seek help?,Will the protein in the urine cause kidney problems in the long run, and how should we monitor it?,Is there any risk of permanent nerve damage, and how can we prevent it?,Are there any clinical trials or new treatments we should know about?
Common questions about Imerslund-Gräsbeck syndrome
What is Imerslund-Gräsbeck syndrome?
Imerslund-Gräsbeck syndrome (IGS), also known as megaloblastic anemia 1 or juvenile selective vitamin B12 malabsorption, is a rare inherited condition that prevents the body from properly absorbing vitamin B12 (cobalamin) from food in the intestines. Vitamin B12 is essential for making healthy red blood cells and keeping the nervous system working properly. Without enough B12, the body produces abnormally large, poorly functioning red blood cells — a condition called megaloblastic anemia — which leads to tiredness, weakness, and pale skin. Many children with IGS also have a kidney problem call
How is Imerslund-Gräsbeck syndrome inherited?
Imerslund-Gräsbeck syndrome follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Imerslund-Gräsbeck syndrome typically begin?
Typical onset of Imerslund-Gräsbeck syndrome is infantile. Age of onset can vary across affected individuals.
Frequently asked questions about Imerslund-Gräsbeck syndrome
Auto-generated from canonical disease facts (Orphanet, OMIM, ClinicalTrials.gov, openFDA, NPPES). Not a substitute for clinical guidance.
What is Imerslund-Gräsbeck syndrome?
Imerslund-Gräsbeck syndrome is a rare disease catalogued in international rare-disease ontologies (Orphanet ORPHA:35858, OMIM 261100). It is typically inherited as autosomal recessive. Age of onset is generally infantile. For verified primary sources, see the UniteRare Imerslund-Gräsbeck syndrome page.
How is Imerslund-Gräsbeck syndrome inherited?
Imerslund-Gräsbeck syndrome follows autosomal recessive inheritance. Genetic counseling is recommended for affected families to understand recurrence risk in offspring and the likelihood of unaffected siblings being carriers. Variants in the underlying gene(s) may be identified via clinical genetic testing.
Are there FDA-approved treatments for Imerslund-Gräsbeck syndrome?
Approved treatments for Imerslund-Gräsbeck syndrome are tracked from openFDA and DailyMed primary sources. Many rare diseases have no specific FDA-approved therapy; for those, supportive care and management of complications form the basis of clinical care. Orphan-drug-designation status is noted where applicable.
Are there clinical trials for Imerslund-Gräsbeck syndrome?
Active clinical trials for Imerslund-Gräsbeck syndrome are tracked daily from ClinicalTrials.gov. Trial availability changes frequently; check the UniteRare trial listings for the current count and recruitment status. Sponsors of rare-disease research often welcome inquiries even when a trial is not actively recruiting at a given moment.
How do I find a specialist for Imerslund-Gräsbeck syndrome?
Verified Imerslund-Gräsbeck syndrome specialists are identified through ClinicalTrials.gov principal-investigator records, peer-reviewed publication authorship (via PubMed), and the NPPES NPI registry. NORD-designated Centers of Excellence and NIH-affiliated rare-disease clinics are also tracked. UniteRare's specialist directory is updated continuously as new evidence becomes available.
See full Imerslund-Gräsbeck syndrome page for complete clinical details, sources, and verified-specialist listings.
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