maturity-onset diabetes of the young type 9 (MONDO_0012818, a Monarch Disease Ontology id) is any maturity-onset diabetes of the young in which the cause of the disease is a mutation in the PAX4 gene. Also known as: MODY9, PAX4 maturity-onset diabetes of the young (disease), maturity-onset diabetes of the young (disease) caused by mutation in PAX4, maturity-onset diabetes of the young, type IX.