Photo-Induced Sarcoidosis in a Diabetic Patient Receiving Metformin Hydrochloride

Sarcoidosis can present with a wide range of skin manifestations, occurring in approximately 30% of sarcoidosis patients. However, photosensitivity in cutaneous sarcoidosis is exceedingly rare. This case report details a unique presentation of photosensitive cutaneous sarcoidosis, its diagnosis, and treatment. A 65-year-old woman presented with numerous erythematous lesions on her eyelids, persisting for 5 months despite treatments with fexofenadine hydrochloride and topical steroids. Her medical history included diabetes mellitus and dyslipidemia, managed with rosuvastatin, metformin, and a combination of teneligliptin and canagliflozin. After discontinuation of rosuvastatin due to suspected interstitial granulomatous dermatitis, her lesions remained unchanged. Clinical examination revealed annular plaques on sun-exposed areas, and skin biopsy showed noncaseating granulomas with eosinophilic infiltration. Elevated serum ACE, calcium, and soluble interleukin-2 receptor levels supported a diagnosis of cutaneous sarcoidosis. Lesions were resistant to systemic and topical steroid treatments, prompting suspicion of photosensitivity. Photo testing identified UVB sensitivity during metformin use, which resolved after discontinuation of the drug. The patient's lesions improved 1 week after stopping metformin, enabling prednisone tapering without recurrence. This case highlights metformin as a potential photosensitizing agent in cutaneous sarcoidosis. While the relationship between diabetes mellitus and sarcoidosis remains unclear, chronic inflammation in diabetes may influence sarcoidosis progression. In cases of refractory cutaneous sarcoidosis despite systemic steroid treatment, it is crucial to consider the coexistence of photosensitivity, particularly drug-induced photosensitivity. Therefore, carefully reviewing the patient's medication history is essential for accurate diagnosis and management.