Scleromyxedema

Article written and reviewed by Dr Luca Moretti

Scleromyxedema is a rare systemic cutaneous mucinosis characterized by a generalized papular and sclerodermoid eruption, dermal mucin, fibroblast proliferation and fibrosis, generally associated with a monoclonal gammopathy but not necessarily with an overt hematologic neoplasm. Also known as scleromucinosis, scleromyxedema differs from pretibial myxedema because thyroid dysfunction is absent and because of its marked tendency toward systemic progression.

The associated gammopathy is most often MGUS, frequently IgG lambda; myeloma or other hematologic neoplasms are much less common. A direct causal role of the paraprotein has not been demonstrated.

From an epidemiologic perspective, scleromyxedema is extremely rare, with several hundred cases reported in the international literature. The mean age at onset is between the fifth and seventh decades of life, with a slight male predominance. Monoclonal gammopathy is frequent, whereas coexistence of an overt hematologic neoplasm is uncommon and must be assessed according to the clinical setting.

Etiology, pathogenesis and pathophysiology

The etiology of scleromyxedema is complex and not fully understood. The most common association is with a monoclonal gammopathy, often IgG lambda, but the direct pathogenetic role of the paraprotein remains unproven. An overt hematologic neoplasm may coexist, but the association does not demonstrate causality; reports involving solid tumors are anecdotal.

No specific risk factors for scleromyxedema have been defined. No environmental, infectious or autoimmune factors are clearly known to be associated with disease onset.

The pathogenesis of scleromyxedema is undefined. An interaction between the monoclonal component and dermal fibroblasts has been hypothesized: serum from some patients may stimulate fibroblasts in vitro, but purified monoclonal immunoglobulin has not shown the same effect and its causal role has not been proven. Increased mucin production, fibroblast proliferation and dermal fibrosis are the main pathologic findings; involvement of TGF-β, PDGF and other profibrotic cytokines remains hypothetical.

At the pathophysiologic level, the disease is distinguished by the coexistence of abundant mucin deposits between dermal collagen fibers, fibroblast proliferation and increased collagen density. Progressive mucinous infiltration and fibrosis may extend to skeletal muscles, fascia, internal organs and the central nervous system, producing a multisystem and potentially fatal disorder. The concentration of the monoclonal component does not show a consistent correlation with the clinical severity of scleromyxedema.

Clinical manifestations

Scleromyxedema typically presents with sclerotic papules that are firm, flesh-colored or yellowish, symmetrically distributed and progressively coalesce into indurated, thickened plaques. The papules, usually 2 to 5 mm in diameter, are arranged in lines or reticular patterns, giving the skin surface a rough or orange-peel appearance. Preferred sites are the face, particularly the glabella, nose, forehead and malar regions, the neck, dorsal hands, arms and upper trunk, whereas the scalp and palmoplantar regions are usually spared.

Skin thickening is often progressive and causes diffuse sclerosis, with loss of elasticity, restricted joint movement and, in the most severe cases, joint contractures and reduced function of the hands and extremities. The skin becomes hard, shiny, adherent to the underlying tissues and difficult to fold. Facial involvement may produce a fixed expression, the so-called “leonine facies”, and may cause dysarthria or difficulty chewing in advanced cases.

One of the distinctive features of scleromyxedema is the frequent presence of systemic manifestations, which are absent in most other cutaneous mucinoses. Internal organ involvement may manifest as esophageal dysmotility with dysphagia and regurgitation, proximal myopathy with weakness and muscle pain, Raynaud phenomena, restrictive heart disease due to myocardial infiltration, pleural effusions or pericardial effusions and, less frequently, restrictive respiratory failure related to pulmonary fibrosis.

The nervous system may be involved with peripheral neuropathies, often polyneuritic in pattern, or, in rare but dramatic cases, with rapidly progressive encephalopathy characterized by confusion, altered consciousness, seizures and coma. So-called “scleromyxedema encephalopathy” is one of the most severe complications and is frequently associated with a poor prognosis if not recognized and treated promptly.

Nonspecific systemic signs such as marked fatigue, low-grade fever, unintentional weight loss and abnormalities related to the gammopathy or to therapy are common and should be interpreted separately.

Overall, the clinical picture is highly polymorphic and variable in severity, ranging from predominantly generalized cutaneous manifestations to rapidly progressive forms with multiorgan involvement, which are often fatal without targeted and timely treatment.

Investigations and diagnosis

The diagnosis of scleromyxedema requires a multidisciplinary approach integrating a detailed history, careful physical examination, laboratory investigations, imaging and, above all, cutaneous histopathology and a complete hematologic evaluation. Clinical suspicion arises in the presence of symmetric skin thickening with sclerotic evolution, associated with characteristic papules and systemic manifestations in an adult, particularly when a monoclonal gammopathy is known or suspected.

Histopathologic examination of the skin is essential and typically shows marked mucin deposition between collagen fibers in the reticular dermis, fibroblast proliferation and increased collagen fiber density, without marked inflammation or an eosinophilic infiltrate. Alcian blue staining confirms the presence of acidic mucopolysaccharides.

Laboratory tests frequently identify a serum monoclonal gammopathy, particularly IgG lambda, detectable by serum protein electrophoresis and immunofixation. The search for the monoclonal component should also include urine to exclude Bence Jones proteinuria. Hematologic assessment should characterize the clone and determine whether multiple myeloma, Waldenstrom macroglobulinemia or other hematologic neoplasms are present, using bone marrow aspiration and biopsy, serum free light-chain measurement and, when necessary, cytogenetic analysis.

Other tests include thyroid function assessment, which is usually normal, acute-phase proteins, liver and kidney function indices and autoimmune investigations to exclude other causes of cutaneous sclerosis or generalized mucinoses. Imaging and additional investigations are performed to document organ involvement or when indicated by specific clinical suspicion.

Diagnosis is based on integration of the clinical, histologic and laboratory features organized in the criteria proposed by Rongioletti and Rebora:

• Generalized papular and sclerodermoid eruption
• Histologic triad of mucin deposition, fibroblast proliferation and fibrosis
• Presence of monoclonal gammopathy, usually IgG lambda
• Absence of thyroid dysfunction

Timely diagnosis is essential not only to start specific therapy but also to manage potentially fatal complications, especially in rapidly progressive forms or those with neurologic involvement.

Treatment and prognosis

The treatment of scleromyxedema aims to control cutaneous and systemic manifestations. High-dose intravenous immunoglobulin is the most widely used first-line systemic treatment; clone-directed therapy is reserved for selected cases or for a hematologic neoplasm with an independent indication for treatment.

Management should be multidisciplinary and tailored to the severity of organ involvement. Treatment of any concomitant neoplasm follows the relevant hematologic indications and does not automatically replace therapy for scleromyxedema.

For cutaneous manifestations and systemic complications, the most effective approach is high-dose intravenous immunoglobulin (IVIg), which has been shown in several studies to be the preferred treatment for controlling papules, cutaneous sclerosis and systemic symptoms, particularly in the absence of contraindications and in patients at neurologic risk. The benefit of IVIg may be transient and repeated cycles may be required to maintain the response.

Other therapeutic options include systemic corticosteroids, which provide partial and transient benefit and carry substantial adverse effects when used long term. Immunosuppressive drugs such as methotrexate, cyclophosphamide or azathioprine, and the immunomodulatory agent thalidomide, have been used with variable success, generally in combination with IVIg or in patients refractory to conventional therapies.

In selected cases, autologous transplantation of hematopoietic stem cells has achieved durable remission of cutaneous and systemic manifestations in selected patients with severe or refractory disease.

The role of targeted therapies is still under study, with reports of efficacy for rituximab (anti-CD20), the proteasome inhibitor bortezomib and inhibitors of profibrotic cytokines in refractory or particularly aggressive cases.

The prognosis of scleromyxedema depends largely on the severity of systemic involvement and the response to treatment. In patients who achieve an adequate response to IVIg and, when present, control of a concomitant hematologic neoplasm, survival and quality of life improve substantially. However, in rapidly progressive forms with neurologic or multiorgan involvement, prognosis remains poor, with high short-term mortality in the absence of effective therapy.

Regular multidisciplinary follow-up is essential, with clinical, laboratory and instrumental monitoring to assess the course of the cutaneous disease, possible recurrence of the monoclonal component and the development of systemic complications or treatment-related adverse effects.

Complications

The complications of scleromyxedema are closely related both to the extent and progression of the cutaneous disease and to systemic complications and treatment effects. Persistent fibroblast activation and mucin deposition may lead to potentially fatal multiorgan involvement, making clinical management particularly complex.

Among the most frequent complications is central neurologic involvement, which may manifest as acute or subacute encephalopathy with cognitive changes, seizures, confusion and, in the most severe cases, coma. This condition, known as “scleromyxedema encephalopathy”, is associated with a very poor prognosis and is often resistant to conventional therapies.

Muscular and fascial involvement frequently causes myopathy and progressive weakness, with motor difficulties and risk of prolonged immobilization. In advanced cases, sclerosis may extend to the respiratory and pharyngeal muscles, leading to restrictive respiratory failure, dysphagia and aspiration.

Cardiac complications such as restrictive cardiomyopathy, arrhythmias and pericardial effusions are common and may progress to worsening heart failure. Renal and pulmonary involvement, often subtle, may further impair the general condition and worsen prognosis.

Opportunistic infections represent an important risk, especially in patients receiving immunosuppressive treatment or in the presence of documented immunodeficiency. Bacterial, viral and fungal infections may complicate the course and contribute to morbidity and mortality, particularly in relation to treatment-induced immunosuppression.

The associated monoclonal gammopathy should be monitored according to its own independent hematologic risk; scleromyxedema does not itself imply transformation to leukemia, lymphoma or myelodysplastic syndromes.

Quality of life is often markedly impaired because of chronic fatigue, functional limitation, cutaneous and joint pain, weight loss and psychological disorders related to the chronicity and severity of the disease.

References
1. Rongioletti F, Rebora A. Updated classification of papular mucinosis, lichen myxedematosus, and scleromyxedema. Journal of the American Academy of Dermatology. 44, 2, 2001, 273-281.
2. Rongioletti F. Lichen myxedematosus (papular mucinosis): new concepts and perspectives for an old disease. Seminars in Cutaneous Medicine and Surgery. 25, 2, 2006, 100-104.
3. Cokonis Georgakis CD et al. Scleromyxedema. Clinics in Dermatology. 24, 6, 2006, 493-497.
4. Blum M et al. Scleromyxedema: a case series highlighting long-term outcomes of treatment with intravenous immunoglobulin (IVIG). Medicine (Baltimore). 87, 1, 2008, 10-20.
5. Koronowska SK et al. Scleromyxedema: a rare disorder and its treatment difficulties. Postępy Dermatologii i Alergologii. 30, 2, 2013, 122-126.
6. Atzori L et al. New insights on scleromyxedema. Journal of Scleroderma and Related Disorders. 4, 2, 2019, 118-126.
7. Cárdenas-Gonzalez RE et al. Lichen myxedematosus: a rare group of cutaneous mucinosis. Anais Brasileiros de Dermatologia. 94, 4, 2019, 462-469.
8. Mahévas T et al. Plasma cell-directed therapies in monoclonal gammopathy-associated scleromyxedema. Blood. 135, 14, 2020, 1101-1110.
9. Haber R et al. Scleromyxedema treatment: a systematic review and update. International Journal of Dermatology. 59, 10, 2020, 1191-1201.
10. Knobler R et al. Consensus statement on the diagnosis and treatment of sclerosing diseases of the skin, Part 2: Scleromyxoedema and scleroedema. Journal of the European Academy of Dermatology and Venereology. 38, 7, 2024, 1281-1299.