Failure to thrive is an early symptom of the imerslund Gräsbeck syndrome.

Purpose: The Imerslund-Gräsbeck syndrome (IGS) is a rare inherited disorder characterized by a megaloblastic anemia due to a selective vitamin B12 malabsorption in association with a mild proteinuria. Usually recurrent infections, gastrointestinal complaints, and pallor are presenting symptoms. We report two cases of IGS with an unusual presentation.

Patients and methods: Two girls are described with the Imerslund-Gräsbeck syndrome who had a failure to thrive as a presenting symptom without infections or gastrointestinal complaints. The diagnosis of IGS was based on marked macrocytic anemia, very low serum vitamin B12 levels, abnormal Schilling urinary excretion test results, and mild proteinuria. When parenteral vitamin B12 was started, a rapid catch-up growth was seen in both girls.

Conclusions: The absence of well-known causes of failure to thrive, such as recurrent infections and gastrointestinal complaints, favors the concept that the metabolic disturbances caused by an isolated cobalamin deficiency as seen in IGS causes a failure to thrive.