Novel compound heterozygous variants in lectin mannose-binding 2-like gene identified in a Chinese autosomal recessive mental retardation-52(MRT52)patient with phenotype expansion

To the Editor:Autosomal recessive mental retardation-52(MRT52,OMIM:616887)was first reported in 2016 and is characterized by global developmental delay,[1]severe intellectual disability(ID),speech disorder,and seizures,but no dysmorphic features.[1,2]MRT52 is caused by a homozygous mutation in the vesicular integral membrane protein 36 kDa(VIP36)-like protein,which is also named lectin mannose-binding 2-like(LMAN2L)gene(OMIM:609552).[3]Nufer et al[4]mapped the LMAN2L gene to chromosome 2q11.2.Although the exact LMAN2L function is not clear,evidence suggests that the LMAN2L gene encodes a transmembrane protein(TM)located in the endoplasmic reticulum(ER).