Anomalous large unique muscle belly of flexor digitorum superficialis and the absence of palmaris longus in the forearm.

Anomalies of muscles of the upper extremity are frequently encountered and anatomic variations of the flexor digitorum superficialis (FDS) muscle-tendon unit are frequently reported by anatomists and clinicians. FDS anomalies can be in forms of tendon interconnections, substitution, absence or muscle belly variations and most of the times the anomalies of FDS produce few clinical symptoms. We report a rare and unusual case of FDS anomaly with a unique and large muscle belly. The deformity is type V according to the classification of Elliot et al. in which the muscle belly extends to four digits (the index, middle, ring and little finger) in the right hand of patient and there is absence of the palmaris longus tendon. The hand surgeon should be able to realise all variations of the FDS tendon and should be prepared for unexpected findings during surgery.