Absence of the inferior portion of the trapezius muscle in three family members

Quantitative Anatomy of the Trapezius Muscle in the Human Fetus

“…Furthermore, Poland's syndrome, characterized by thorax deformity and syndactyly, is associated with the absence of copious skeletal muscles, the pectoralis major in particular, muscles in the upper limb, and occasionally encompasses anomalies of the trapezius [2]. The isolated lack of the trapezius may result from an incomplete failure of occipital or cervical somites [3,15,16]. During embryogen- esis both mechanical and inflammatory reasons are responsible for the absence of the trapezius.…”