Phocomelia is a rare birth defect characterised by severe limb deformities.  Bones of the upper limbs are shortened or absent, and fingers may be fused. In extreme cases, both upper and lower limb bones are absent so that the hands and feet are attached to the body directly constituting what is known as tetraphocomelia. Phocomelia can either be genetically inhereted or drug-induced. In its genetic form it is transmitted as an autosomal recessive trait which is linked to several chromosomal mutations. Spontaneous gene mutations have also been recognised.

Drug-induced cases of phocomelia syndrome can be mostly associated with maternal ingestion of the drug thalidomide by expectant females (sometimes referred to as thalidomide syndrome). Thalidomide was developed in Germany in 1954 and gained widespread use as treatment for morning sickness in early pregnancy.It was also used as a sedative and cough suppressant. It has been recently used in the management of multiple myeloma, erythema nodosum leprosum and is also being investigated for the treatment of a variety of other conditions including inflammatory and immunological diseases and some cancers. It was recognised as a cause for severe congenital deformities, and was withdrawn from the market worldwide between 1961 and 1962.