Hypertrophy of palmaris longus muscle, a rare anatomic aberration.

The palmaris longus muscle (PLM) is considered to be a phylogenetically degenerate muscle. For many authors, this may be the cause of its great variability. The loss of function in the PLM makes it an important muscle in plastic and reconstructive surgery. During a study of PLM agenesis rate in the Hungarian population, a 22-year-old female showed an unusual pattern of muscles in her left forearm, which was found to be a hypertrophied PLM. The hypertrophied muscle was causing symptoms of median and ulnar nerve compression.