During routine anatomical dissection of the anterior compartment of the forearm region, a tendinous-musculo-tendinous muscle was found on the right forearm originating from the medial aspect of the radial shaft and inserting into the palmar aponeurosis. The muscle coursed deep to pronator teres muscle, parallel and lateral to the flexor digitorum superficialis muscle and deep to the tendon of the flexor carpi radialis. Distally, the muscle tendon coursed under the flexor retinaculum and it was invested with the median nerve by a common fascial sheath. The muscle was found in the presence of an intact palmaris longus muscle. Because of its attachments and course, the muscle was classified as a palmaris profundus muscle. Several subtypes of palmaris profundus muscles have been reported. To our knowledge this is the first case of a palmaris profundus with a tendon originating from the medial aspect of the radial diaphysis, a muscular portion and a distal tendon inserting in the palmar aponeurosis. Anatomical variations of muscles in the flexor compartment of the forearm may have functional, diagnostic, and surgical implications.
