deformity deformity a deformity, dysmorphism, or dysmorphic feature is a major abnormality of an organism that makes a part of the body appear or function differently than how it is supposed to. chinese circus performer with craniofacial deformity from craniosynostosis, 1927 a deformed sucker cluster on an arm of an octopus causes deformity can be caused by a variety of factors: arthritis and other rheumatoid disorders chronic application of external forces, e.g. artificial cranial deformation chronic paresis, paralysis or muscle imbalance, especially in children, e.g. due to poliomyelitis or cerebral palsy complications at birth damage to the fetus or uterus fractured bones left to heal without being properly set (malunion) genetic mutation growth or hormone disorders infection reconstructive surgery following a severe injury, e.g. burn injury deformity can occur in all organisms: frogs can be mutated due to ribeiroia (trematoda) infection. plants can undergo irreversible cell deformation insects, such as honeybees, can be affected by deformed wing virus fish can be found with scoliosis due to environmental factors mortality case of acephalus holoacardiacus - born without a head. was birthed alongside a healthy twin. in many cases where a major deformity is present at birth, it is the result of an underlying condition severe enough that the baby does not survive very long. the mortality of severely deformed births may be due to a range of complications including missing or non-functioning vital organs, structural defects that prevent necessary function, high susceptibility to injuries, abnormal facial appearance, or infections that eventually lead to death. in some cases, such as that of twins, one fetus is brought to term healthy, while the other faces major, even life-threatening defects. an example of this is seen in cattle, referred to as amorphous globosus. in mythology there are many instances of mythological characters showing signs of a deformity. descriptions of mermaids may be related to the symptoms of sirenomelia. the irish mythology includes the fomorians, who are almost without exception described as being deformed, possessing only one of what most have two of (eyes, arms, legs, etc.) or having larger than normal limbs. hephaestus, of greek mythology, was born with a club foot.