Familial Selective Vitamin B₁₂ Malabsorption (Imerslund-Grasbeck Syndrome) in a Pool of Turkish Patients

Abstract

Thirty-six patients with Imerslund-Gräsbeck syndrome are presented. The mean ages at presentation and diagnosis were 4.7 ± 3.7 years and 7.2 ± 4.2 years, respectively. The mean hemoglobin level was 5.8 ± 2.2 g/dL, the mean cell volume was 104.9 ± 11.6 fL, the white blood cell count was 4479 ± 2022/mm3, and the serum vitamin B₁₂ level was 96.9 ± 73 pg/mL. At diagnosis, 5 of the 36 patients, aged 5 to 16 years, had neurologic symptoms. All the patients had severe megaloblastic changes in bone marrow precursor cells. Proteinuria was detected in 78% of them. Patients with proteinuria had a younger age of onset (P < 0.0001) and diagnosis (P < 0.001) compared with those without proteinuria. In all patients, vitamin B₁₂ excretion unbound to intrinsic factor after a flushing dose of vitamin B₁₂ was lower than normal, and there was no appreciable correction in urinary vitamin B₁₂ excretion after binding of intrinsic factor. The impairment of vitamin B₁₂ absorption studies in Schilling tests; however, showed great variation among patients. Serum haptoglobin values were close to zero in all patients, indicating the presence of that intravascular hemolysis in Imerslund-Gräsbeck syndrome. Variations among patients in the age of presentation, degree of impairment of vitamin B₁₂ absorption, and presence or absence of proteinuria suggest a heterogeneity in etiology of Imerslund-Gräsbeck syndrome at the molecular level.

Key Words:

• Imerslund-Gräsbeck syndrome
• megaloblastic anemia
• proteinuria