Molybdenum Cofactor Deficiency, Complementation Group a, also known as sulfite oxidase deficiency due to molybdenum cofactor deficiency type a, is related to molybdenum cofactor deficiency, complementation group c and molybdenum cofactor deficiency, complementation group b, and has symptoms including opisthotonus An important gene associated with Molybdenum Cofactor Deficiency, Complementation Group a is MOCS1 (Molybdenum Cofactor Synthesis 1), and among its related pathways/superpathways are Metabolism and Regulation of expression of SLITs and ROBOs. Affiliated tissues include eye and brain, and related phenotypes are macrocephaly and intellectual disability