Abstract
Background: Morbihan disease (MD) is a rare dermatological condition, which is characterized by rosaceous lymphedema or erythematous edema of the middle and upper thirds of the face. To date, the underlying pathogenetic mechanisms of MD remains unclear. Although MD is considered a late-stage manifestation of rosacea, it has been reported to exist as an initial presentation, in the absence of other features of rosacea.
Case Presentation: A 27-year-old female with a history of hypothyroidism, presented with a chronic solid, persistent, facial swelling for 4 years without rosacea symptoms. The patient wore a face cover for religious and social reasons, and therefore her face was not exposed to direct sunlight. Based on the clinical findings, a preemptive diagnosis of MD was established, and the patient was started on oral Isotretinoin with significant improvement. Histopathology of the left cheek revealed perifollicular lymphocyte and histocyte infiltration and mild dermal fibrosis; no granuloma or malignancy was found. After 36 months of treatment, there was an overall 65%-70% improvement since the initial visit and the patient was pleased with her results.
Conclusion: In contrast to published reports, the formation of epithelioid cell granuloma as well as mast cell infiltration were not observed in presented case. The diverse histopathological features of MD are most likely attributed to its varying underlying inflammatory triggers. The presence of MD without rosacea features supports the argument that MD represents a separate disease process.

Key words: Morbihan disease, Morbihan syndrome, rosaceous lymphedema, lymphedematous rosacea, facial edema