Specific lymph node involvement in scleromyxedema: a new diagnostic entity for hypermetabolic lymphadenopathy.

Scleromyxedema is a generalized skin disease mostly associated with monoclonal gammopathy. In its chronic course, it can lead to systemic disorders related to mucin deposits in organs. We describe here specific lymph node involvement, hitherto not reported in scleromyxedema. A 68-year-old man with a 1-year history of micropapular eruption and skin sclerosis involving the neck, trunk, hands, and face was diagnosed with scleromyxedema associated with IgG kappa monoclonal gammopathy. Enlarged mediastinal lymph nodes found on thoracic X-ray and computed tomography scan were hypermetabolic on positron emission tomography. Lymph node biopsy showed partial nodal infiltration by numerous fibroblasts surrounded by mucin and collagen deposits, the same being observed on the skin biopsy. Lymph node and skin lesions both improved after intravenous immunoglobulin and corticosteroid treatment. Lymph node involvement in scleromyxedema should be considered in the etiological diagnosis of hypermetabolic, enlarged lymph nodes, especially if monoclonal gammopathy is associated.