Dysmelia
Dysmelia (from Gr. δυσ- dys, "bad" + μέλ|ος mél|os, "limb" + Eng. suff. -ia) is a congenital disorder of a limb resulting from a disturbance in embryonic development.
Types
Dysmelia can refer to
- missing (aplasia) limbs: amelia, oligodactyly, congenital amputation
- malformation of limbs: shortening (rhizomelia or mesomelia), ectrodactyly, phocomelia, meromelia, syndactyly, brachydactyly, club foot
- too many limbs: polymelia, polydactyly, polysyndactyly
Occurrence rate
Birth defects involving limbs occur in 1 per 1000.[citation needed]
Causes
Dysmelia can be caused by
- inheritance of abnormal genes, e.g. polydactyly, ectrodactyly or brachydactyly, symptoms of deformed limbs then often occur in combination with other symptoms (syndromes)
- external causes during pregnancy (thus not inherited), e.g. via amniotic band syndrome
- teratogenic drugs (e.g. thalidomide, which causes phocomelia) or environmental chemicals
- ionizing radiation (nuclear weapons, radioiodine, radiation therapy)
- infections
- metabolic imbalance