Arthrogryposis multiplex congenita involving both upper extremities may resemble bilateral brachial plexus palsy. The characteristics of arthrogryposis multiplex congenita that distinguish it from brachial plexus palsy are: (1) the presence of skin pits at the wrists and (2) the permanent nature of the arm position (Figure 167.1). Patients with brachial plexus palsy do not have skin pits and the abnormal position is only present when the neonate attempts to move the arm.

Figure 167.1.— Typical arm position and wrist pit characteristic of arthrogryposis multiplex congenita.