Reticular erythematous mucinosis
Lesions manifest as midline confluent erythematous papules and plaques forming a reticular (net-like) configuration. REM appears to be a disorder of photosensitivity, as a preceding history of intense sun exposure is often elicited. Ultraviolet A (UVA) and ultraviolet B (UVB) both appear to provoke lesions, and further sun exposure usually worsens the condition. In addition, heat, perspiration, and radiation may exacerbate REM. Hormonal influences also seem to play an etiologic role, as oral contraceptives, menses, and pregnancy have been reported to trigger and exacerbate it.
While REM is thought to be limited to the skin, approximately 20% of cases may have systemic comorbidities, such as thrombocytopenia, diabetes mellitus, malignancies, and thyroid disease. Lupus serology is positive only in a small percentage of patients.
Plaque-like cutaneous mucinosis is considered synonymous with REM or is considered to belong to a spectrum of midline mucinosis. Clinically, it is more likely to present as erythematous infiltrated papules and plaques occurring over the midline of the back and chest.
L98.5 – Mucinosis of the skin
238946004 – Reticular erythematous mucinosis
Differential Diagnosis & Pitfalls
- Tumid lupus – Chronic cutaneous lupus variant with erythematous to violaceous papules, plaques, and nodules. The lesions lack the reticulate quality of REM. Tumid lupus most often arises on the face, extensor forearms, shoulders, V-neck of chest, and back. There is considerable overlap with REM as the condition is histologically identical, usually has negative serology, and is for the most part limited to the skin.
- Cutaneous lupus mucinosis – Seen only in males of Japanese descent, it appears as skin-colored to red papules and nodules on the chest, giving the appearance of a lumpy chest. May precede or coincide with the development of systemic lupus erythematosus, most often with renal and articular manifestations.
- Confluent and reticulated papillomatosis – Reticulate hyperpigmentation of central chest; most often seen in adolescence. Lesions may be subtly papillated yet fail to have the infiltrated look / feel of REM and are more tan-brown than red.
- Mycosis fungoides – Two cases have been reported in which mycosis fungoides clinically mimicked REM.
- Dermatomyositis – The "V" sign is erythema that occurs higher up on the chest in a "V" configuration.