Imerslund-Gräsbeck Syndrome

from Wikipedia, the free encyclopedia
Classification according to ICD-10
D51.1 Vitamin B- 12 -Mangelanämie by selective vitamin B12 malabsorption with proteinuria
ICD-10 online (WHO version 2019)

The imerslund-gräsbeck syndrome (IGS) (also: Imerslund-Najman-Gräsbeck syndrome , Imerslund syndrome or selective vitamin B 12 - (cobalamin) malabsorption with proteinuria ) is a rare (1: 200,000 births) autosomal - recessive inherited selective disorder of the absorption of vitamin B 12 in the terminal ileum . The disease was first described in 1960 by the Oslo pediatrician Olga Imerslund (1907–1987) and the Helsinki laboratory doctor Ralph Gräsbeck (1930–2016).

Pathophysiology

The genetic cause of the disease is a fault in the receptor protein for the complex of cobalamin (vitamin B 12 ) and the intrinsic factor . There can be a mutation of two genes: the cubilin gene ( CUBN ) on chromosome 10 or the amnionless gene ( AMN ) on chromosome 14 . Both proteins are components of a receptor that binds the complex of vitamin B 12 and intrinsic factor in the small intestine (terminal ileum ) and thus enables vitamin B 12 to be absorbed into the blood. They are also involved in the reabsorption of protein from the primary urine in the renal tubules . The absence or impaired function of this receptor makes it impossible to absorb vitamin B 12 , the deficiency of which usually leads to symptoms of the disease from early childhood.

Symptoms

In addition to a (not always present) protein excretion by the kidneys ( proteinuria ), all symptoms of vitamin B 12 deficiency are present: megaloblastic ("pernicious") anemia , failure to thrive and grow, the tendency towards infection and neurological disorders. The symptoms are pronounced due to the absolute lack of vitamins. The decreased B 12 absorption found in the absorption test is not increased by the intrinsic factor. The symptoms first appear from the 4th month up to several years after the birth.

therapy

The disease can only be treated by parenteral administration (by injection) of vitamin B 12 . With a lifelong adequate substitution, those affected stay healthy for decades. The proteinuria persists without there being any disease of the kidneys in the strict sense. Since the genetically defective proteins are also responsible for the absorption of other micronutrients in the intestine, thorough absorption tests are usually carried out to determine whether other nutrients in addition to vitamin B 12 must also be supplied parenterally. As part of the therapy, genetic counseling for further family planning is also required. Relatives of an affected person should also be checked for signs of vitamin B 12 deficiency.

literature

Web links