Dysmelia

Dysmelia (from the Greek dys (δυσ-), "bad" + mélos (μέλος), "limb" + English suffix -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 e.g. tibial or radial aplasia
 * malformation of limbs: shortening (micromelia, rhizomelia or mesomelia), ectrodactyly, phocomelia, meromelia, syndactyly, brachydactyly, club foot
 * extra limbs: polymelia, polydactyly, polysyndactyly
 * others: tetraamelia, hemimelia, symbrachydactyly

Occurrence rate
Birth defects involving limbs occur in 0.69 per 1000.

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

Syndromes with dysmelia

 * 2p15-16.1 microdeletion syndrome
 * Achard syndrome
 * Ackerman syndrome
 * Acrocallosal syndrome
 * Acropectoral syndrome
 * Adams–Oliver syndrome
 * Aglossia adactylia
 * Amniotic band syndrome
 * Apert syndrome
 * Autosomal recessive Robinow syndrome
 * Basel–Vanagaite–Sirota syndrome (Microlissencephaly-Micromelia syndrome)
 * Campomelic dysplasia
 * Cardiofaciocutaneous syndrome
 * Catel–Manzke syndrome
 * Cenani–Lenz syndrome
 * Corneodermatoosseous syndrome
 * Diploid triploid mosaic
 * Ectrodactyly–ectodermal dysplasia–cleft syndrome
 * Edwards syndrome
 * Ellis–Van Creveld syndrome
 * Fibular dimelia diplopodia syndrome (Leg duplication mirror foot syndrome)
 * Greig cephalopolysyndactyly syndrome
 * Haas syndrome
 * Hanhart syndrome
 * Holt–Oram syndrome
 * Humeroradial synostosis
 * Johnson–Munson syndrome
 * Joubert syndrome
 * McKusick–Kaufman syndrome
 * Mermaid syndrome
 * Mesomelia-Synostoses syndrome (8q13 microdeletion syndrome)
 * Microgastria
 * Myhre syndrome
 * Nager acrofacial dysostosis
 * Neu–Laxova syndrome
 * Patau syndrome
 * Pfeiffer syndrome
 * Poland syndrome
 * Radial aplasia
 * Roberts SC-Phocomelia syndrome (Phocomelia syndrome)
 * Rubinstein–Taybi syndrome
 * Silver–Russell syndrome
 * Split-hand split-foot malformation (SHFM)
 * TAR syndrome (thrombocytopenia with absent radius)
 * Tetra-amelia syndrome
 * Ulbright–Hodes syndrome
 * VACTERL association
 * Wallis–Zieff–Goldblatt syndrome