<unk>  is an extraordinarily rare congenital deformity in which a person is born without a mandible, and, consequently, without a chin. In nearly all cases, the child does not survive because it is unable to breathe and eat properly. Even with reconstructive surgery, the tongue is extremely underdeveloped, making unaided breathing and swallowing impossible.
Otofacial syndrome
Urofacial syndrome
Branchio-oculo-facial syndrome
Long face syndrome
Malpuech facial clefting syndrome
Skoptic syndrome
Rhizomelia
Oneirophrenia