Research shows that Biermer’s disease, a vitamin B12 deficiency caused by autoimmune stomach damage, may increase the risk of dangerous blood clots in rare cases. According to Gram Research analysis of this 2026 case report, a 57-year-old patient with undiagnosed Biermer’s disease developed blood clots in his stomach veins, with elevated homocysteine levels serving as a connecting factor. When B12 levels drop too low, homocysteine accumulates in the blood, which damages blood vessel walls and promotes clotting. While this connection is uncommon, doctors should screen patients with unexplained blood clots for B12 deficiency.
A case report from 2026 describes a 57-year-old man who developed dangerous blood clots in his stomach blood vessels, which turned out to be caused by an undiagnosed vitamin B12 deficiency disease called Biermer’s disease. According to Gram Research analysis, this rare condition occurs when the body’s immune system attacks cells in the stomach that help absorb vitamin B12, leading to dangerously low B12 levels. The case highlights an important connection: when B12 levels drop too low, they can increase a harmful substance in the blood called homocysteine, which makes blood clots more likely to form. Doctors should consider checking for Biermer’s disease in patients with unexplained blood clots.
Key Statistics
A 2026 case report documented a 57-year-old patient with undiagnosed Biermer’s disease who developed splanchnic venous thrombosis (blood clots in stomach veins), highlighting a rare but serious connection between vitamin B12 deficiency and blood clot formation.
Research shows that Biermer’s disease causes vitamin B12 deficiency by destroying the stomach’s ability to produce intrinsic factor, a protein essential for B12 absorption, which can lead to elevated homocysteine levels that increase blood clotting risk.
The case report identified mild hyperhomocysteinemia (elevated homocysteine) as a connecting factor between Biermer’s disease and venous thrombosis, suggesting that B12 deficiency may increase clotting risk through this blood chemical pathway.
The Quick Take
- What they studied: Whether Biermer’s disease (a vitamin B12 deficiency caused by immune system problems) can increase the risk of dangerous blood clots forming in stomach blood vessels
- Who participated: One 57-year-old man from the Mediterranean region who had a history of thyroid disease and developed unexpected blood clots
- Key finding: A patient with undiagnosed Biermer’s disease developed blood clots in his stomach blood vessels, with elevated homocysteine levels (a blood chemical that increases clotting risk) being a connecting factor
- What it means for you: If you have unexplained blood clots or symptoms of vitamin B12 deficiency (fatigue, numbness, weakness), ask your doctor to check for Biermer’s disease. This is a rare connection, so don’t assume you have it, but awareness helps doctors diagnose faster.
The Research Details
This is a case report, which means doctors documented the medical story of one patient to highlight an unusual or important clinical finding. The 57-year-old patient came to the hospital with blood clots in the veins that drain blood from his stomach and intestines—a serious condition called splanchnic venous thrombosis. Doctors ran many tests to figure out what caused the clots, including blood work, imaging studies, and genetic testing.
During their investigation, they discovered two important findings: the patient had mildly elevated homocysteine (a blood chemical linked to clotting) and undiagnosed Biermer’s disease. Biermer’s disease is an autoimmune condition where the body’s immune system mistakenly attacks cells in the stomach lining that produce intrinsic factor, a protein needed to absorb vitamin B12 from food. Without intrinsic factor, vitamin B12 cannot be properly absorbed, leading to severe deficiency.
The doctors connected these findings: the B12 deficiency from Biermer’s disease likely caused the elevated homocysteine, which then increased the risk of blood clots. This case is important because it shows a rare but serious connection between these conditions that doctors should watch for.
Case reports are valuable because they alert the medical community to unusual patterns or connections that might not be obvious. When one patient develops an unexpected combination of conditions, it can help doctors recognize similar patterns in other patients. This case matters because it suggests that patients with Biermer’s disease may need extra monitoring for blood clot risk, and patients with unexplained blood clots should be screened for B12 deficiency.
This is a single case report, which is the lowest level of scientific evidence. One patient’s story cannot prove that Biermer’s disease causes blood clots in everyone. However, case reports serve an important purpose: they raise awareness and generate hypotheses for future research. The strength of this report is the thorough investigation—doctors ruled out many other causes before identifying Biermer’s disease. The main limitation is that we cannot generalize from one person to a larger population. More research with many patients would be needed to confirm this connection.
What the Results Show
The patient presented with blood clots in the splanchnic veins (the veins that drain blood from the stomach, intestines, and spleen). This is a serious condition that can cause severe abdominal pain and complications. When doctors investigated the cause, they found that standard risk factors for blood clots—like cancer, recent surgery, or genetic clotting disorders—were not present.
However, blood tests revealed two important abnormalities: the patient had elevated homocysteine levels (though only mildly elevated) and very low vitamin B12 levels. Further testing showed that the patient had antibodies against intrinsic factor, which is the hallmark of Biermer’s disease. This autoimmune disease prevents the stomach from absorbing B12 from food, no matter how much B12 the person eats.
The connection appears to be that chronic B12 deficiency increases homocysteine in the blood. Homocysteine is a naturally occurring amino acid, but when levels get too high, it damages blood vessel walls and makes blood more likely to clot. In this patient, the combination of B12 deficiency and elevated homocysteine likely created the conditions for dangerous blood clots to form.
Once doctors identified Biermer’s disease, they started treating the patient with B12 injections (since the stomach cannot absorb B12 from food or pills). This treatment addresses the root cause of the problem.
The patient also had a history of Graves’ disease, an autoimmune thyroid condition. This is noteworthy because it suggests the patient may have a tendency toward autoimmune diseases in general. People with one autoimmune disease are at higher risk for developing others, which may explain why this patient developed both Graves’ disease and Biermer’s disease.
Biermer’s disease is a well-known cause of vitamin B12 deficiency, and elevated homocysteine is a recognized risk factor for blood clots. However, the specific connection between Biermer’s disease and splanchnic venous thrombosis (blood clots in stomach veins) is uncommon and not well-documented in medical literature. This case report adds to our understanding by showing that doctors should consider this connection when evaluating patients with unexplained blood clots. It also highlights that autoimmune diseases may cluster together in some patients.
This is a single case report involving one patient, so we cannot conclude that Biermer’s disease causes blood clots in everyone who has it. Many people with Biermer’s disease never develop blood clots. We don’t know if this patient had other risk factors we’re not aware of, or if the combination of conditions was simply coincidental. The patient’s homocysteine elevation was only mild, so it’s unclear how much it contributed to clot formation. To truly understand the connection, researchers would need to study many patients with Biermer’s disease and track how many develop blood clots over time. Additionally, this case cannot determine whether B12 treatment alone will prevent future clots or if additional anticoagulation therapy is necessary.
The Bottom Line
If you have been diagnosed with Biermer’s disease, work with your doctor to ensure you’re receiving regular B12 injections and that your B12 levels are being monitored. If you experience unexplained abdominal pain, swelling, or symptoms of blood clots, inform your doctor about your B12 deficiency. If you have unexplained blood clots, ask your doctor to check your B12 levels and homocysteine levels as part of the investigation. These recommendations are based on a single case, so they should be discussed with your healthcare provider rather than viewed as definitive guidelines. Confidence level: Low to Moderate (based on case report evidence).
Patients with diagnosed Biermer’s disease should be aware of this potential connection and discuss it with their doctors. Patients with unexplained blood clots should ask their doctors to investigate B12 deficiency as a possible contributing factor. Doctors treating patients with autoimmune diseases should be alert to the possibility of multiple autoimmune conditions occurring together. People with a family history of Biermer’s disease or autoimmune conditions may want to discuss screening with their healthcare provider. This case is less relevant for people without B12 deficiency or known autoimmune conditions.
If you have Biermer’s disease and start B12 injections, it typically takes several weeks to months to restore B12 levels to normal. Once B12 levels improve, homocysteine levels should gradually decrease, which may reduce clotting risk over time. However, if blood clots have already formed, they require immediate medical treatment and may need anticoagulation therapy (blood thinners). The timeline for preventing future clots depends on how quickly B12 levels normalize and how well the underlying condition is managed.
Frequently Asked Questions
What is Biermer’s disease and how does it cause vitamin B12 deficiency?
Biermer’s disease is an autoimmune condition where the body’s immune system attacks stomach cells that produce intrinsic factor, a protein needed to absorb vitamin B12 from food. Without intrinsic factor, B12 cannot be absorbed, leading to severe deficiency that requires B12 injections for treatment.
Can vitamin B12 deficiency cause blood clots?
Vitamin B12 deficiency can increase homocysteine levels in the blood, a chemical that damages blood vessel walls and promotes clotting. This 2026 case report documents one patient where B12 deficiency from Biermer’s disease contributed to dangerous blood clots, though this connection is rare.
What symptoms should I watch for if I have Biermer’s disease?
Watch for B12 deficiency symptoms: fatigue, weakness, numbness or tingling in hands and feet, shortness of breath, and pale skin. Also watch for blood clot warning signs: severe abdominal pain, swelling, redness, or chest pain. Report any new symptoms to your doctor immediately.
How is Biermer’s disease treated?
Biermer’s disease is treated with regular vitamin B12 injections, usually given monthly, since the stomach cannot absorb B12 from food or oral supplements. Blood tests monitor B12 levels to ensure the injections are working effectively and preventing deficiency symptoms.
Should people with Biermer’s disease be screened for blood clots?
While blood clots are uncommon in Biermer’s disease, this case report suggests doctors should be alert to the possibility. If you have Biermer’s disease and develop unexplained abdominal pain or other clot symptoms, inform your doctor so they can investigate. Routine screening isn’t standard unless symptoms appear.
Want to Apply This Research?
- If you have Biermer’s disease, track your B12 injection dates and any symptoms of deficiency (fatigue, numbness, weakness, shortness of breath). Record any abdominal pain or swelling that could indicate blood clot formation. Log these monthly to share with your doctor.
- Set reminders for your scheduled B12 injections and never skip doses. Keep a symptom diary noting energy levels, tingling sensations, and any unusual pain. Report new or worsening symptoms to your doctor immediately rather than waiting for your next appointment.
- Use the app to track B12 injection dates and set reminders. Create alerts for warning signs of blood clots (severe abdominal pain, swelling, redness). Monitor energy and neurological symptoms monthly. Share this data with your healthcare provider at each visit to ensure your B12 levels are adequately controlled and to catch any complications early.
This article describes a single case report and should not be used for self-diagnosis or self-treatment. Biermer’s disease and blood clots are serious medical conditions requiring professional diagnosis and treatment. If you experience symptoms of vitamin B12 deficiency (fatigue, numbness, weakness) or blood clots (severe abdominal pain, swelling, chest pain), contact your healthcare provider immediately. Do not delay seeking medical care based on this information. Always consult with your doctor before making changes to your treatment plan or starting new medications. This content is for educational purposes only and is not a substitute for professional medical advice.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.