This revealed both brothers had a homozygous stop-gain variant NM_001081.3:c.4689_4690delTAinsAT; p.(Cys1563Ter) in exon 31 of the gene CUBN. Biallelic variants in CUBN have previously been associated with Imerslund-Grasbeck Syndrome (Megaloblastic anemia-1, Finnish type (MIM: 261100)) and one reported case of isolated proteinuria [6–8]. This evidence concerns the gene CUBN and Imerslund-Grasbeck syndrome.