Achondroplasia is a genetic disorder with an autosomal dominant pattern of inheritance whose primary feature is dwarfism.[3] It is the most common cause of dwarfism[4] and affects about 1 in 27,500 people.[3] In those with the condition, the arms and legs are short, while the torso is typically of normal length.[3] Those affected have an average adult height of 131 centimetres (4 ft 4 in) for males and 123 centimetres (4 ft) for females.[3] Other features can include an enlarged head with prominent forehead (frontal bossing)[3] and underdevelopment of the midface (midface hypoplasia).[6] Complications can include sleep apnea or recurrent ear infections.[3] Achondroplasia includes the extremely rare short-limb skeletal dysplasia with severe combined immunodeficiency.