Standard of Care Treatment for IGS

Because Imerslund-Gräsbeck syndrome (IGS) is caused by a permanent genetic inability to absorb Vitamin B12 from food, the goal of treatment is straightforward: bypass the gut entirely to deliver the vitamin directly where it is needed ^[1][2]. While the diagnosis of a lifelong condition can be daunting, the treatment for IGS is generally very effective ^[3].

The Standard of Care: B12 Injections

The accepted treatment for IGS is lifelong Vitamin B12 (cobalamin) replacement therapy ^[4][5]. Because the receptor in the small intestine is broken, traditional dietary Vitamin B12 or routine supplements cannot be relied upon ^[2].

• The Route: Injections—delivered into the muscle (intramuscular) or just under the skin (subcutaneous)—are the most reliable way to ensure the body receives enough B12 ^[6][7]. Hydroxocobalamin and cyanocobalamin are common forms used.
• The Schedule: Treatment typically begins with a loading phase to quickly refill the body’s depleted stores ^[8]. Once levels are stabilized, your child will transition to a maintenance phase ^[5]. The product, dose, route, loading intensity, and maintenance interval vary with age, severity, local practice, and the individual’s response ^[1]. Your specialist will determine the specific regimen. Do not change the dosage or skip injections without consulting your care team. If you miss a dose, contact your team for instructions on what to do next.

A Note on Oral Therapy

You may hear about high-dose oral Vitamin B12 as an alternative. While some B12 can seep across the gut lining even without the receptor, high-dose oral treatment is a specialist-supervised option for selected patients, not something to trial independently ^[9]. Most pediatric IGS success stories are based on injections, and oral therapy requires extremely strict adherence and frequent blood monitoring to ensure levels don’t drop ^[4][9]. If oral therapy fails, the deficiency can return, potentially causing irreversible neurological damage before symptoms are noticed ^[10].

Response to Treatment

Once treatment begins, you can expect to see improvements:

• Blood Recovery: Hematologic response often begins with a reticulocyte response within days, and hemoglobin improvement over the following weeks, though full normalization may take longer ^[5][8].
• Neurological Gains: Improvements in coordination or energy levels can begin within weeks ^[11]. However, neurological recovery is highly variable and depends on how severe and how long the deficiency was present. Recovery may take months or remain incomplete, so do not expect rapid full recovery of walking or coordination in all cases ^[11][6].

Why the Protein Persists

A common point of confusion is that while the anemia goes away, the proteinuria (protein in the urine) almost always persists ^[2][4].

This does not mean the B12 treatment is failing. It happens because the same genetic defect that breaks the gut receptor also breaks the mechanism in the kidneys that normally reabsorbs filtered protein ^[12][13]. While this protein loss is a permanent feature of IGS, evidence suggests that kidney function is usually preserved ^[14][1]. Your child’s care team will recommend regular kidney monitoring as a standard precaution ^[4].