<P> A number of genetic disorders affect the hand . Polydactyly is the presence of more than the usual number of fingers . One of the disorders that can cause this is Catel - Manzke syndrome . The fingers may be fused in a disorder known as syndactyly . Or there may be an absence of one or more central fingers--a condition known as ectrodactyly . Additionally, some people are born without one or both hands (amelia). </P> <P> There are several cutaneous conditions that can affect the hand including the nails . </P> <P> The autoimmune disease rheumatoid arthritis can affect the hand, particularly the joints of the fingers . </P> <P> Some conditions can be treated by hand surgery . These include carpal tunnel syndrome, a painful condition of the hand and fingers caused by compression of the median nerve, and Dupuytren's contracture, a condition in which fingers bend towards the palm and cannot be straightened . A similar condition to this is where some of the fingers cannot be flexed due to injury to the ulnar nerve . </P>

Five bones in the palm of the hand