Imerslund-Grasbeck disease, also called familial selective vitamin B12 malabsorption, is a rare inherited disorder that causes deficiencies in vitamin B12. The body is unable to absorb this vitamin from foods, such as fish, shellfish, meats, and dairy products.
Symptoms of the disorder usually develop four months to several years after birth. Because vitamin B12 is needed to produce healthy blood cells, patients with Imerslund-Grasbeck disease typically produce fewer and abnormally large red blood cells (called megaloblasts). This condition is commonly called megaloblastic anemia.
Some patients may also develop frequent infections and mild proteinuria (high amounts of protein in the urine) with no signs of kidney disease. If left untreated, patients may develop neurological problems, which may lead to permanent brain damage.
Researchers estimate that Imerslund-Grasbeck disease affects only six out of 1,000,000 people. To date, only about 300 cases have been reported worldwide, primarily in eastern Mediterranean countries.
Imerslund-Grasbeck disease can be successfully treated with lifelong supplements of vitamin B12. Because the patient is unable to absorb the vitamin in the small intestine, it must be injected.
Although treatment corrects the vitamin B12 deficiency, proteinuria is still present in patients who experience this condition. The symptoms of proteinuria are not a cause for concern because proteinuria will not worsen over time, and it does not indicate kidney damage.
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