Lupus Erythematosus Tumidus in the Differential Diagnosis of Facial Erythema.

Lupus erythematosus is an autoimmune disease that frequently presents with dermatologic manifestations. When it is limited to the facial area, it is difficult to distinguish from other inflammatory diseases. Among the differential diagnoses of facial erythema, lupus erythematosus tumidus (LET) is an uncommon entity that represents a subtype of lupus erythematosus. It is characterized as a photosensitive dermatosis with a favorable clinical course and prognosis. A 32-year-old female patient presented with dermatosis localized to the face, specifically in the frontal and maxillary regions, characterized by persistent facial erythema with papular eruptions over a two-year period. Initially diagnosed as rosacea, she received multiple treatments without clinical improvement. Subsequently, histopathological findings led to the diagnosis of LET, a form of intermittent cutaneous lupus erythematosus that occurs much less frequently than other forms of cutaneous lupus. It presents with a relapsing course associated with sun exposure, histopathologically characterized by superficial and deep perivascular and periadnexal lymphocytic infiltrates with dermal mucin deposition. It may clinically mimic other skin disorders. Therefore, skin biopsies are indicated in various clinical scenarios when histopathologic information is required to make a diagnosis and establish the definitive treatment plan.