Scleromyxedema is a rare skin and systemic mucinosis that is usually associated with monoclonal gammopathy (MG). In this French, multicenter, retrospective study of 33 patients, we investigated the clinical and therapeutic features of MG-associated scleromyxedema. Skin molecular signatures were analyzed using a transcriptomic approach. Skin symptoms included papular eruptions (100%), sclerodermoid features (91%), and leonine facies (39%). MG involved an IgG isotype in all patients, with a predominant λ light chain (73%). Associated hematologic malignancies were diagnosed in 4/33 patients (12%) (smoldering myeloma, n=2; chronic lymphoid leukemia, n=1; and refractory cytopenia with multilineage dysplasia n=1). Carpal tunnel syndrome (33%), arthralgia (25%) and dermato-neuro syndrome (DNS) (18%) were the most common systemic complications. One patient with mucinous cardiopathy died of acute heart failure. Intravenous immunoglobulin (HDIVig) treatment alone or in combination with steroids appeared to be quite effective in nonsevere cases (clinical complete response achieved in 13/31 patients). Plasma cell-directed therapies using lenalidomide and/or bortezomib with dexamethasone and HDIVig led to a significant improvement in severe cases (HDIVig-refractory or cases with central nervous system or cardiac involvement). The emergency treatment of DNS with combined plasmapheresis, HDIVig, and high-dose corticosteroids induced the complete remission of neurological symptoms in 4/5 patients. Quantitative reverse transcriptase-PCR (RT-PCR) analysis of 6 scleromyxedema skin samples showed significantly higher profibrotic pathway levels (transforming growth factor β (TGFβ) and collagen-1) than in healthy skin. Prospective studies targeting plasma cell clones and/or fibrotic pathways are warranted for long-term scleromyxedema management.

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