Morbihan Disease: A Rare Case of Periorbital Bilateral Edema with Histopathological Findings of Chronic Inflammation and Demodex Localization.

BACKGROUND Morbihan disease, also known as Morbihan syndrome, is a rare medical condition characterized by chronic facial edema predominantly affecting the upper two-thirds of the face. Despite being recognized in medical literature for decades, its true prevalence and underlying pathophysiology remain poorly understood. Various hypotheses, including impaired lymphatic drainage, abnormal vascular permeability, immune dysregulation, and inflammatory reactions to demodex infestation, have been proposed to explain the etiology. CASE REPORT We present a case of a 61-year-old man with organized periocular edema of the upper third of the face, ultimately leading to Morbihan disease diagnosis. The patient underwent a midface lift, allowing for tissue retrieval for histopathological examination of the eyelid edematous skin, which revealed chronic inflammation, ectasia of small lymphatic vessels, and features of demodex intrafollicular localization. These findings were not specific, but consistent with the diagnostic hypothesis. The patient was referred to a rheumatologist for further evaluation and treatment. He did not respond well to systemic corticosteroids and immunosuppressive therapy. Rather, this resulted in extension of the edema to the upper eyelid. The patient opted not to undergo further treatment. CONCLUSIONS Morbihan disease is often misdiagnosed due to its rarity and overlapping clinical features with other facial conditions. Its management is challenging and can require a combination of medical and surgical interventions. Systemic corticosteroids, immunosuppressive agents, and topical treatments have had varying success. Surgical procedures, such as blepharoplasty or laser therapy, can be considered in severe cases. Early recognition and appropriate management are crucial to improving patient outcomes and quality of life.