Achondroplasia dwarfism occurs as a sporadic mutation in approximately 85% of cases (associated with advanced paternal age) or may be inherited in an autosomal dominant genetic disorder that is a common cause of dwarfism. If both parents of a child have achondroplasia, and both parents pass on the mutant gene, then it is very unlikely that the homozygous child will live past a few months of its life. The disorder itself is caused by a change in the DNA for fibroblast growth factor receptor 3 which causes an abnormality of cartilage formation. Achondroplastic dwarfs have short stature, with an average adult height of 131 cm (4 feet, 3½ inches) for males and 123 cm (4 feet, ½ inch) for females.