Hypoplasia of the maxilla (HP_0000327, a Human Phenotype Ontology entry) is abnormally small dimension of the Maxilla. Usually creating a malocclusion or malalignment between the upper and lower teeth or resulting in a deficient amount of projection of the base of the nose and lower midface region. Also known as: Decreased size of maxilla, Decreased size of upper jaw, Hypoplasia of upper jaw bones, Hypoplastic maxillary bones, Maxillary deficiency, Maxillary hypoplasia, Maxillary micrognathia, Maxillary retrognathia.