Thousand are the patients that undergo infiltration of filler composed of hyaluronic acid with effects that are generally considered acceptable, with the idea, however, that in all cases the product is reabsorbable, and there are no important risks of either local or systemic toxic reactions.

The caution to be used is that necessary for any type of filler commonly employed and the technique of infiltration, after a brief course of learning, is easy performed. The problems related to product itself are rather rare and reported only occasionally in the literature.

What we wish to report is precisely a clinical case that we happened to treat that I believe has never been reported in the literature.

It concerns a female patient, twenty six years old, that came to our attention because she noticed the appearance of a formation of a cystic nature in the infra-zygomatic region, exactly in the same site where an infiltration of hyaluronic acid had been performed a few months previously in another centre.

Consequently, we proceeded with surgery for removal of the neoformation through an external incision: the histological examination of the capsula indicated it to be a cutaneous metaplastic synovial cyst.

The cause of cutaneous metaplastic synovial cysts is unclear, but a traumatic history usually precedes its onset. Synovial-like metaplasia also has been described around prostheses and breast implant capsules and may occur in post surgical cutaneous scars, unrelated to prostheses or implants.
The cyst in the zygomatic region, having arisen after the local infiltration of hyaluronic acid, (with no history of local trauma) constitute an element of a relationship that seems obvious.

What is only to imagine is how and why this may have taken place.

Such a complication, therefore, might be interesting to be considered as a possible side effect, if confirmed also from reports of other Colleagues, when one decides to increase the volume of certain regions of the face using hyaluronic acid filler.

F. Inchingolo 1-4, A. D. Inchingolo1, M. Tatullo 2, M. Marrelli 4 , A.M. Inchingolo 3, F. Carbotti 1, A. Palladino 1, M. De Carolis 1, V. Angelini 1 , A.D. Inchingolo1, G. Dipalma1-4
Department of Odontostomatology and Surgery, University of Bari, Bari, Italy
Private Doctor in Dental Sciences
Department of Odontostomatology and Surgery, University of Milano, Milano, Italy
Department of Maxillofacial Surgery, Calabrodental Srl, Crotone, Italy