Here we report monoallelic missense variants that are absent for gnomAD and result in substitution of Arg51 or, in a single case, Phe52 residues of MAB21L1 in families with severe aniridia [MIM 106210], a phenotype associated with monoallelic mutations in PAX6 [MIM 607108], and/or microphthalmia. Here, MAB21L1 is linked to isolated aniridia.