Taking it on the shin: Part two

By Warren R. Heymann, MD, FAAD
June 7, 2023
Vol. 5, No. 23

Last week pretibial pruritic papular dermatitis was reviewed as an underrecognized entity on the shins. Today the focus is on obesity-associated lymphedematous mucinosis (OALM), another disorder that you have likely seen, but perhaps did not recognize.

Unsurprisingly, when dermatologists see infiltrative plaques in the pretibial regions, pretibial myxedema (PM, more accurately termed thyroid dermopathy) comes to mind. Although characteristically appearing after treatment of Graves’ disease, PM may develop in hypothyroid or euthyroid patients. PM is characterized by non-pitting edema and skin-colored to violaceous nodules or plaques. When observed in its characteristic location, the differential diagnosis includes lymphedema, lipodermatosclerosis, and OALM. (1)

In their seminal article 30 years ago, Somach et al investigated whether histologic characteristics can distinguish pretibial mucinosis secondary to Graves’ disease from cases unassociated with thyroid disease. Biopsy specimens compatible with PM were reviewed; these included 12 cases of pretibial mucinosis with documented Graves’ disease, and six cases of pretibial mucinosis without evidence of Graves’ disease. Ten specimens interpreted as compatible with stasis dermatitis were also evaluated for histologic characteristics, including the possible presence of mucin. The authors found that features distinguishing between pretibial mucinosis associated with Graves’ disease and pretibial mucinosis without Graves’ disease included preservation of a zone of normal-appearing collagen in the superficial papillary dermis (12/12 with Graves’ disease, 0/6 without), mucin deposition in the reticular dermis (12/12 with Graves’ disease, 0/6 without), lack of mucin deposition in the superficial papillary dermis (11/12 with Graves’ disease, 1/6 without), angioplasia (2/12 with Graves’ disease, 6/6 without), and the presence of hemosiderin (2/12 with Graves’ disease, 6/6 without). Mucin deposition in the papillary dermis was found in 6 of 10 specimens interpreted as stasis dermatitis. The authors concluded that pretibial mucinosis may result from stasis or Graves’ disease and that histologic differences allow for accurate differentiation. (2)

In 2003, Sáez-Rodríguez et al observed “localized lichen myxoedematosus (papular mucinosis)” in the suprapubic region of two women with morbid obesity. Both patients had complete resolution of the lesions within a year of a low-calorie diet. (3)

Three years later, Tokuda et al reported 3 patients with pretibial mucinosis without thyroid disease, their abstract stating: “The patients were characterized clinically by morbid obesity and bilateral lower extremity pitting oedema with gradual and painless onset, and that did not involve the feet and ankles. Vesicles, semitranslucent papules or a woody plaque were found on the shins. Histologically, patients showed characteristic features of epidermal atrophy with effacement of the rete ridge pattern, separation of collagen bundles associated with oedema with stellate to linear fibroblasts, upward-running increased capillary and small vessels with haemosiderin deposition, and mucin deposition at the superficial papillary dermis and around the vessels. We propose that the present cases of ‘chronic obesity lymphoedematous mucinosis’ belong to the clinical entity of pretibial mucinosis.” (4)

Rongioletti et al described 5 similar cases in middle-aged to elderly patients (4/5 women), coining the phrase OALM. (5) Other studies have confirmed the histological findings of epidermal atrophy, dermal edema, angioplasia with thick-walled vertically running dermal vessels embedded in a fibromyxoid matrix, staining positive with Alcian Blue pH 2.5 denoting the presence of superficial dermal mucin (glycoaminoglycan). (6)

Although the pathogenesis of OALM has not been fully elucidated, it is hypothesized that hypoxia may be a key factor. Lymphatic stasis due to obesity causes a local hypoxia with subsequent increased production of mucin from fibroblasts in response to reduced oxygen tension. Due to the defect in lymphatic drainage, which may be compounded by venous insufficiency, interstitial deposition of plasmatic proteins, including albumin, and coagulation factors worsen edema, decreasing local oxygen delivery and stimulating fibroblasts to further synthesize and deposit glycosaminoglycans. Mechanistically, so-called pretibial stasis mucinosis, which occurs in the context of venous insufficiency, is presumably the same entity. (7) In venous insufficiency-associated dermal mucinosis the mucinous deposits also distinctly surround eccrine glands and pilosebaceous units.

Therapeutically, weight reduction is the principal strategy. Compression may improve lymphostasis and venous insufficiency; if severe, vascular surgery is an option. (8)

In my experience, OALM — especially the stasis mucinosis subset — is common. Recognizing the disorder may help get our patients on the right track toward weight reduction.

Point to Remember: Obesity-associated lymphedematous mucinosis and stasis mucinosis can be differentiated from euthyroid pretibial myxedema. Weight reduction and compression may improve these disorders.

Our expert’s viewpoint

Franco Rongioletti
Full Professor of Dermatology and Chairman
Vita-Salute - S.Raffaele University, Milan

Although lymphedema and stasis dermatitis are not uncommon manifestations associated with obesity, obesity-associated lymphedematous mucinosis and pretibial stasis mucinosis are uncommon and newly recognized disorders occurring in obese patients or in patients with chronic lymphedema and venous insufficiency. This is not a matter of semantics as a low-calorie diet and compression coincide with a clinical improvement.

1. Renzi MA, Jr, Heymann WR. Pretibial myxedema. In Lebwohl MG, Heymann WR, Coulson IH, Murrell DF (eds). Treatment of Skin Disease, Sixth edition. Elsevier, London, 2022, pp 688-691.

2. Somach SC, Helm TN, Lawlor KB, Bergfeld WF, Bass J. Pretibial mucin. Histologic patterns and clinical correlation. Arch Dermatol. 1993 Sep;129(9):1152-6. doi: 10.1001/archderm.129.9.1152. PMID: 8363399.

3. Sáez-Rodríguez M, García-Bustínduy M, López-Alba A, Noda-Cabrera A, Guimerá-Martín-Neda F, Dorta-Alom S, Escoda-García M, Fagundo-González E, Sánchez-González R, Martín-Herrera A, García-Montelongo R. Localized lichen myxoedematosus (papular mucinosis) associated with morbid obesity: report of two cases. Br J Dermatol. 2003 Jan;148(1):165-8. doi: 10.1046/j.1365-2133.2003.05117.x. PMID: 12534614.

4. Tokuda Y, Kawachi S, Murata H, Saida T. Chronic obesity lymphoedematous mucinosis: three cases of pretibial mucinosis in obese patients with pitting oedema. Br J Dermatol. 2006 Jan;154(1):157-61. doi: 10.1111/j.1365-2133.2005.06901.x. PMID: 16403111.

5. Rongioletti F, Donati P, Amantea A, Ferrara G, Montinari M, Santoro F, Parodi A. Obesity-associated lymphoedematous mucinosis. J Cutan Pathol. 2009 Oct;36(10):1089-94. doi: 10.1111/j.1600-0560.2008.01239.x. Epub 2009 Feb 10. PMID: 19222694.

6. Ferreli C, Pinna AL, Pilloni L, Corbeddu M, Rongioletti F. Obesity-Associated Lymphedematous Mucinosis: Two Further Cases and Review of the Literature. Dermatopathology (Basel). 2018 Feb 6;5(1):16-20. doi: 10.1159/000486305. PMID: 29719826; PMCID: PMC5920949.

7. Ferreli C, Atzori L, Rongioletti F. Obesity-associated lymphedematous mucinosis and stasis mucinosis. Clin Dermatol. 2021 Mar-Apr;39(2):229-232. doi: 10.1016/j.clindermatol.2020.10.014. Epub 2020 Oct 16. PMID: 34272015.

8. Rongioletti F. New and emerging conditions of acquired cutaneous mucinoses in adults. J Eur Acad Dermatol Venereol. 2022 Jul;36(7):1016-1024. doi: 10.1111/jdv.17983. Epub 2022 Feb 17. PMID: 35124832.

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