Unilateral absence of the thoracic part of the trapezius muscle

The absence of some muscles, such as pectoralis major, serratus anterior an d quadratus femoris have been described, however the absence of trapezius, either in isolation or in association with other structures, is not often o bserved. In this case study, we present a case of partial absence of the le ft trapezius muscle in an adult black male cadaver, which had a large apone urosis replacing the ascending fibres and some of the transverse fibres of the muscle. Histological analysis showed the presence of a few muscle fibre s in the aponeurosis. From a functional viewpoint, it is possible that this individual would have had difficulty in moving his shoulder, especially du ring flexion. abduction and circumduction of the arm.