15 Years of Intermittent Therapy With Hydroxychloroquine Without Any Loss of Efficacy in Reticular Erythematous Mucinosis.

Reticular erythematous mucinosis (REM) is a rare dermatological condition characterized by erythematous, reticulated patches and plaques with a slightly infiltrated appearance. REM is classified among cutaneous mucinoses, which are characterized by the accumulation of mucin in the subcutaneous tissues, leading to the formation of characteristic reticulated patches on the skin. The pathogenesis is still debated, but the association with sun exposure seems to play an important role. We present the case of a 54-year-old individual with a history of recurrent erythema on the chest and back. The patient came to our attention in 2007 due to a worsening of symptoms after sun exposure. On clinical examination, the patient presented with pruritic, erythematous patches with a reticulated appearance. A biopsy was performed, which showed the presence of a moderate lymphocytic infiltrate in the dermis, with a perivascular and periappendageal distribution, consisting mainly of T lymphocytes, and deposits of mucin in the superficial dermis, dissecting the collagen bundles. A diagnosis of REM was made, and the patient began treatment with hydroxychloroquine 200 mg per day, with rapid improvement of symptoms. Considering the resolution of symptoms, the therapy was discontinued after 3 months. The patient remained in remission until the following summer when the condition recurred, requiring a new cycle of hydroxychloroquine therapy. The patient has experienced recurrences over the past 15 years during the summer, which responded to hydroxychloroquine therapy, consistently achieving rapid symptom resolution without ever experiencing loss of efficacy or side effects.