Reticular erythematous mucinosis: a review of patients' characteristics, associated conditions, therapy and outcome in 25 cases

Summary Background Reticular erythematous mucinosis (REM) is an uncommon disease, the nosology and specific characteristics of which are controversial because most reports deal with single cases or small series. Objectives To describe the characteristics of patients with REM regarding demographics, clinical and pathological features, comorbidities, treatment and course. Methods A retrospective and prospective study was conducted on 25 patients diagnosed with REM in the setting of university‐affiliated dermatology departments and dermatopathology centres. Results Of the 25 patients with REM, 16 were women (sex ratio 2 : 1) and the mean age was 46 years. The roles of sun exposure and oral contraceptives were ambiguous. Associated diseases included hypertension (n = 4), malignancies (n = 3), autoimmune diseases (n = 3) and Borrelia infection (n = 1). Immunological studies (including serology and direct immunofluorescence) were noncontributory. The response to antimalarial treatment was good in > 80% of cases. Worsening or recurrence of the lesion after treatment discontinuation, or in the course of the disease, occurred in 31% of patients. Conclusions We present the largest REM case series to date. The reticular pattern with involvement of the midline of the chest and back, the predilection for middle‐aged women, the controversial relationship with photosensitivity and the possible association with other conditions such as malignancies and thyroid dysfunctions are the main characteristics that makes REM a recognizable disease. What's already known about this topic? Reticular erythematous mucinosis (REM) is an uncommon disease, the nosology and specific characteristics of which are controversial because most reports deal with single cases or small series. What does this study add? We report one of the largest case series of REM to date. We highlight the reticular pattern in REM; the predilection for middle‐aged women; the ambiguous role of photosensitivity; the possible association with other conditions such as malignancies and thyroid dysfunctions; and the good response to antimalarials, with possible relapses. Together, these factors make REM a recognizable disease.