Loss‐of‐function variants in MOCS2 are linked with autosomal recessive molybdenum cofactor deficiency B (MOCODB), which leads to clinical manifestations such as poor feeding, pharmacoresistant epilepsy, severe developmental delay, intracerebral cysts, and complex brain malformations while typically maintaining the brain stem intact. This evidence concerns the gene MOCS2 and sulfite oxidase deficiency due to molybdenum cofactor deficiency type B1.