Acta Dermatovenerol Croat 2019;27(1):16-21 REVIEW Reticular Erythematous Mucinosis: A Rare Cutaneous Mucinosis Amer Ali Almohssen1, Ragha Vasantha Suresh2,Robert A. Schwartz2 1Dermatopathology, State University of New York Downstate Medical School & The Ackerman Academy of Dermatopathology New York City, NY, USA; 2Dermatology and Pathology, Rutgers New Jersey Medical School, Newark, New Jersey, USA Corresponding Author ABSTracT Reticular erythematous mucinosis (REM) is a rare form of pri- Amer Ali Almohssen, MD mary cutaneous mucinosis, most often involving the midline of the upper chest or back in middle-aged women. REM bears clinical and histopatho- Dermatopathology Fellow, State University logic resemblance to lupus erythematosus tumidus (LET), dermatomyosi- of New York tis, scleredema, and lichen myxedematosus. Early recognition and diagno- Downstate Medical School & The Ackerman sis of REM is particularly relevant to exclude the abovementioned diseases, as REM is more benign and has fewer systemic consequences. Academy of Dermatopathology New York City KEY WORDS: reticular erythematous mucinosis, lupus erythematous tu- New York midus, scleredema, dermatomyositis, lichen myxedematosus, papular mu- USA cinosis [email protected] Received: December 27, 2017 Accepted: February 9, 2019 INTRODUCTION The cutaneous mucinoses are a diverse group of pathologic resemblance to lupus erythematosus tu- disorders in which elevated levels of mucin are found midus (LET), dermatomyositis, scleredema, and pap- in the skin, predominantly in the dermis (1). The pri- ular mucinosis. However, recent evidence supports mary cutaneous mucinoses are characterized by mu- the recognition of REM as a distinct entity, based on cin deposition as the major histological feature, and its distinctive clinical and histologic features of this include scleromyxedema, scleredema, and lichen disorder. Therefore, early recognition and diagnosis myxedematosus (papular mucinosis) among others of REM are particularly relevant, as it excludes lupus, (1). Secondary mucinoses are disorders in which mu- scleredema, papular mucinosis or dermatomyositis. cin deposition is an additional finding, and include lu- REM is more benign and has fewer systemic conse- pus erythematous, dermatomyositis and granuloma quences than the abovementioned diseases. annulare (1). Reticular erythematous mucinosis (REM), first de- EPIDemiOLOGY OF REM scribed by Steigleder in 1974. is a rare form of primary REM is also known as plaque-like cutaneous mu- cutaneous mucinosis, most often involving the mid- cinosis or midline mucinosis (3,4). It usually is first line of the upper chest or back in middle-aged wom- evident as a non-scaly eruption of erythematous en (2,3). Within the heterogeneous group of disorders macules and papules in a reticulated pattern most of cutaneous mucinosis, REM bears clinical and histo- commonly over the midline of the chest (3). In rare 16 ACTA DERMATOVENEROLOGICA CROATICA Almohssen et al. Acta Dermatovenerol Croat Reticular erythematous mucinosis 2019;27(1):16-21 cases, REM may also be evident on other sites such as Dermatomyositis (DM) the face, legs, arms, and abdomen (5). Most often, pa- The primary skin lesions of DM are erythematous tients are women in the third and fourth decades of to violaceous papules and plaques, most often locat- life. They often have a relapsing and remitting course, ed symmetrically on the extensor dorsal aspects of with the disease limited to the skin (3,4). the metacarpophalangeal and interphalangeal joints Although the etiology is unknown, fibroblasts (Gottron’s papules), with the second most common of patients with REM have an abnormal response to distribution being a heliotrope eruption of the up- exogenous IL-1b (6). In addition, tubuloreticular in- per eyelids. Both of these skin findings are pathog- clusions have been detected in endothelial cells and nomonic for DM (9). Less commonly, DM may pres- pericytes within the skin lesions (6). The disease is ex- ent with a maculopapular rash that may be related to acerbated by menses, contraceptives, and pregnancy, photosensitivity, which can mimic the skin findings suggesting a possible hormonal basis. Solar exposure seen in REM patients. Other skin findings in DM in- can flare it too, or in some cases improve the disease clude photo-distributed poikiloderma (neck, shawl), course. It may be associated with smoking (7), lupus scalp dermatitis, nailfold telangiectasias, violaceous erythematosus, diabetes mellitus, myxedema, hypo- plaques over the knees and elbows, calcinosis cu- thyroidism, Hashimoto’s thyroiditis, thrombocytope- tis (more in juvenile variant), and mechanic hands nia, monoclonal gammopathy, HIV infection, breast (ragged cuticles, hyperkeratosis, scaling, and fissur- cancer, and colon cancer (3,4). Immunologic distur- ing of distal fingers) (9). The muscular involvement bances and viral infections have also been postulated is clinically characterized by symmetrical, proximal, to be linked with the induction of REM syndrome (7). progressive muscle weakness (9). It is important to Fühler et al. (8) described monozygotic female note that muscular involvement is often seen in DM twins who both presented with REM at almost the patients, and has not been associated with REM. same time in the same location after UV exposure. A study by Edward et al. (10) found that the muci- Familial manifestations of REM syndrome are rare; an nous lesions may be caused by the presence of certain association with a distinct HLA constellation has not serum-derived factors. This work demonstrated that been proven. However, the almost simultaneous ap- serum from patients with DM stimulates both sul- pearance of cutaneous lesions by light provocation at phated glycosaminoglycan and hyaluronic acid syn- identical sites in these twin sisters suggests a genetic thesis by fibroblasts from both control and involved predisposition. skin. In contrast, the fibroblasts from patients with Atci et al. delineated REM involving a mastectomy DM show similar levels of GAG synthesis as control scar, the upper chest, and the midline of the back. fibroblasts in the presence of a control serum. These This patient then underwent a mammary reconstruc- results suggest that these fibroblasts are not activat- tion involving an abdominal skin flap. The abdominal ed, nor contain a population of cells that overexpress skin flap was lesion-free prior to the reconstruction; GAGs. DM is frequently associated with the presence however, after the reconstruction, the abdominal of an underlying malignancy (11). As DM is frequently skin flap demonstrated appearance of REM. As such, associated with the presence of an underlying malig- REM should be included in the differential diagnosis nancy, it is possible that the tumor may be releasing of persistent erythematous patches occurring on scar factors into the serum to promote the development sites. of the characteristic mucinous lesions. DM is primarily treated with steroids, though hy- Differential Diagnosis for REM droxychloroquine, methotrexate, and azathioprine Clinical diagnosis of REM is by exclusion, facili- may also be used (9). Maugers et al. (12) studied the tated by clinical, histopathologic, and laboratory long-term prognosis of patients with DM and found correlation to rule out lupus erythematous tumidus that survival rates were 82.6% at 1 year, 73.9% at 2.66 (LET), papular mucinosis (PM), dermatomyositis (DM) years, 7% at 5 years and 55.4% at 9 years. The main and scleredema (Table 1). Clinically, REM, LET, and DM prognostic factors were old age, cancer, pulmonary can show erythematous plaque-like lesions with sig- interstitial fibrosis and asthenia-anorexia. nificant lack of serologic abnormalities; however, the shape and distribution of lesions aid in distinction. Lupus erythematosus tumidus (LET) REM’s principle lesion is more often a papule than a LET is commonly first evident with erythema- patch or plaque. Its reticulated pattern is distinct and tous, urticarial-like single or multiple plaques with most often involves the skin of chest, less commonly no surface changes such as follicular plugging. They the upper back, with variable photosensitivity. involve sun-exposed areas, especially the face, upper ACTA DERMATOVENEROLOGICA CROATICA 17 Almohssen et al. Acta Dermatovenerol Croat Reticular erythematous mucinosis 2019;27(1):16-21 Table 1. Comparing REM, LET, DM, scleredema, and LM REM LET DM Scleredema LM History Women in 3rd Associated with Underlying Underlying etiology Adults between the or 4th decade of smoking - males malignancy, can also including recent ages of 30 and 80 life; exacerbated and females present with myositis streptococcal years with no race or by oral equally affected infection, gender predominance; contraceptives, hyperparathyroidism, underlying monoclonal menses, and Sjögren syndrome, gammopathy or pregnancy rheumatoid malignancy arthritis, malignant insulinoma, multiple myeloma, HIV infection, diabetes mellitus Physical Non-scaly Erythematous Erythematous to Firm and woody Normochromic or eruption of to violaceous violaceous papules plaques, diffuse, erythematous papules, erythematous plaques or and plaques, most symmetric, ranging from 1 mm to macules and nodules, with often located non-pitting skin 4 mm. The papules are papules in a or without an symmetrically on induration; classically firm and waxy and are reticulated annular pattern the extensor dorsal affects the upper symmetrically arranged, pattern most on sun-exposed aspects