Homozygous mutation in the intrinsic factor gene in a child with severe vitamin B12 deficiency

: A 28 month-old boy was hospitalized with pallor and weight stagnation. He had macrocytic anaemia and pancytopenia due to cobalamin deficiency and a rare homozygous mutation in the intrinsic factor gene. His sister showed similar symptoms at the age of 15 months. The heterozygous father had no symptoms, but did have a low cobalamin level. Gastroscopy with biopsies showed no pathology. All were given monthly cyanocobalamin injections which, however, caused leg cramps. Replacement with monthly hydroxocobalamin was successful.