Doctors discovered a rare genetic condition in a young boy that prevents his body from absorbing vitamin B12 properly. This condition, called Imerslund-Gräsbeck syndrome, is caused by inherited gene mutations that affect how the body processes B12. The boy developed severe anemia (low red blood cells) and protein in his urine starting at age one. When doctors gave him regular B12 injections, his blood counts improved quickly. This case report helps doctors recognize and treat this uncommon condition early, though the protein in the urine remained even after treatment began.

The Quick Take

  • What they studied: A single case of a young boy with a rare genetic disorder that prevents his body from absorbing vitamin B12, leading to severe anemia and protein in his urine.
  • Who participated: One young male patient who started showing symptoms at age one year old, including severe anemia and protein in his urine.
  • Key finding: The boy had a genetic mutation in the AMN gene that prevented his body from absorbing B12. Regular B12 injections quickly improved his red blood cell counts and anemia symptoms.
  • What it means for you: This case helps doctors recognize a rare but treatable genetic condition. If a young child has unexplained severe anemia and protein in their urine, doctors should consider testing for this genetic disorder. However, this is just one patient’s story, so results may not apply to everyone with this condition.

The Research Details

This is a case report, which means doctors documented the medical history and treatment of one specific patient with an unusual condition. The young boy presented with severe anemia (abnormally low red blood cells) and protein appearing in his urine starting at age one. Doctors performed blood tests that showed very low vitamin B12 levels. They then conducted genetic testing to identify the specific gene mutation causing the problem.

The patient was found to carry a mutation in the AMN gene, which is responsible for making a protein that helps the body absorb B12 from food. This genetic mutation prevented his body from properly absorbing B12, even though he was eating normally. Once doctors identified the problem, they started treating him with regular B12 injections, which bypass the absorption problem by delivering B12 directly into the bloodstream.

The doctors followed the patient over time to see how he responded to treatment, measuring his hemoglobin levels (the protein in red blood cells that carries oxygen) and checking for the continued presence of protein in his urine.

Case reports are valuable because they document unusual medical conditions that doctors might not see often. By publishing this case, the doctors help other healthcare providers recognize similar symptoms in their own patients. This can lead to faster diagnosis and treatment for other children with the same rare genetic condition. Additionally, this case shows that regular B12 injections are an effective treatment for this genetic disorder.

This is a single case report, which is the lowest level of scientific evidence. It describes what happened with one patient, but cannot prove that the same results would occur in other patients. However, case reports are important for documenting rare diseases and unusual presentations. The diagnosis was confirmed with genetic testing, which is a reliable method. The main limitation is that this represents only one person’s experience, so the findings cannot be generalized to all patients with this condition.

What the Results Show

The young patient presented with severe macrocytic anemia, which means his red blood cells were abnormally large and his body didn’t have enough of them. This caused symptoms related to low oxygen delivery throughout his body. Blood tests revealed that his vitamin B12 level was very low, which explained the anemia. Genetic testing identified a specific mutation in the AMN gene (the mutation was c.1006 + 34_1007-31 del with duplication of exons 2-3), confirming the diagnosis of Imerslund-Gräsbeck syndrome.

When treatment began with regular B12 injections, the results were dramatic and quick. The patient’s hemoglobin levels (the measure of red blood cells) improved rapidly, and his anemia symptoms resolved. This rapid improvement confirmed that B12 deficiency was the primary cause of his anemia, and that injected B12 could effectively treat the condition by bypassing his body’s absorption problem.

Interestingly, the patient also had protein in his urine (proteinuria), which is unusual because it typically indicates kidney problems. However, in this genetic condition, the protein in the urine appears to be a separate feature of the disease, not caused by kidney damage. Even after B12 treatment improved his anemia, the protein in his urine continued to be present at follow-up visits.

The persistent proteinuria (protein in the urine) despite successful B12 treatment is an important secondary finding. This suggests that the protein in the urine is a separate manifestation of the genetic disorder, not simply a consequence of the B12 deficiency. This indicates that patients with this condition may need monitoring for kidney function even after their anemia is successfully treated. The case demonstrates that Imerslund-Gräsbeck syndrome affects multiple body systems, not just B12 absorption.

Imerslund-Gräsbeck syndrome is a well-documented but rare genetic disorder. Previous medical literature has established that this condition is caused by mutations in either the CUBN or AMN genes. This case report confirms that the AMN gene mutation can cause the typical presentation of the disease and responds well to B12 injections. The finding that proteinuria persists despite B12 treatment aligns with previous understanding that the protein in the urine is a distinct feature of this genetic condition, not simply a consequence of B12 deficiency.

This is a single case report involving only one patient, so the findings cannot be generalized to all people with this condition. Different patients may have different symptoms, disease severity, or treatment responses. The case does not include long-term follow-up data beyond the initial treatment period, so we don’t know how the patient fares over many years. Additionally, case reports cannot establish cause-and-effect relationships or compare different treatment approaches. This case is most valuable for helping doctors recognize the condition, not for determining the best treatment strategies overall.

The Bottom Line

For patients diagnosed with Imerslund-Gräsbeck syndrome: Regular B12 injections are highly recommended (strong evidence from this and other cases) and should be continued for life. Regular monitoring of hemoglobin levels is recommended to ensure the B12 treatment is working. Kidney function monitoring is suggested (moderate confidence) because of the persistent proteinuria seen in this case. For healthcare providers: Consider testing for this genetic disorder in young children with unexplained severe anemia and protein in their urine, especially if family history suggests genetic disease.

This information is most relevant to: Parents of children with unexplained anemia and protein in urine; Healthcare providers caring for children with rare genetic disorders; Patients with confirmed Imerslund-Gräsbeck syndrome and their families. This should NOT be used for self-diagnosis or to replace professional medical evaluation. If your child has anemia or protein in their urine, consult with a doctor for proper testing and diagnosis.

Based on this case, B12 injections can produce rapid improvement in anemia symptoms within weeks to months. However, some features of the condition (like proteinuria) may persist despite treatment. Long-term management requires lifelong B12 injections and regular medical monitoring. The timeline for seeing benefits varies by individual, so discuss realistic expectations with your healthcare provider.

Want to Apply This Research?

  • Track B12 injection dates and hemoglobin levels at each doctor visit. Users should log: injection date, location, dose, and any side effects. At each lab visit, record the hemoglobin level result and date to monitor treatment effectiveness over time.
  • Set reminders for scheduled B12 injections to ensure consistent treatment adherence. Create a calendar alert system for regular lab work appointments to monitor hemoglobin and kidney function. Users can also track energy levels and anemia symptoms daily to correlate with injection schedules.
  • Establish a long-term tracking dashboard showing: B12 injection schedule and adherence, hemoglobin trends over months/years, lab appointment dates and results, and symptom severity ratings. Compare hemoglobin levels before and after injections to visualize treatment effectiveness. Set annual reminders for kidney function screening given the persistent proteinuria in this case.

This case report describes one patient’s experience with a rare genetic disorder. It is not medical advice and should not be used for self-diagnosis. If you or your child experience symptoms of anemia (fatigue, weakness, shortness of breath) or have protein in urine, consult a qualified healthcare provider for proper evaluation and testing. Genetic testing and diagnosis should only be performed by medical professionals. Treatment decisions should be made in consultation with your doctor based on your individual circumstances. This information is educational and does not replace professional medical care.