Guyon's canal syndrome caused by mass effect after chronic dog bite hand injury.

Epidermal inclusion cysts are defined as dermal or subcutaneous epithelial cysts which are filled with keratin and lined with true epidermis. Although exceedingly rare, they can lead to pathological conditions, such as nerve compression syndrome. To the best of our knowledge, this is the first documented case of a 59-year-old woman with ulnar nerve compression at the wrist due to dog bite hand injury. An epidermal inclusion cyst was located adjacent to the ulnar nerve, resulting in significant compression. Notably, no direct connection was observed between the cyst and ulnar nerve. Surgical resection of the cyst led to complete resolution of tingling in the patient's middle and ring fingers. Although uncommon compared to the frequently reported causes of ulnar neuropathy, epidermal inclusion cysts should be considered as a differential diagnosis, particularly in patients with a history of repetitive wrist motion and trauma. A comprehensive diagnostic approach and tailored surgical interventions are needed to ensure good clinical outcomes in such cases.