Scleromyxedema is a rare connective tissue disorder characterized by a generalized lichenoid eruption and sclerodermoid induration with histologic features of dermal mucin deposition. A 44-year-old man presented with a 3-year history of generalized progressive skin thickening and sclerosis. He had diffuse skin-colored to erythematous firm papules coalescing into indurated plaques over his whole body. He had been diagnosed with scleromyxedema from a skin biopsy with monoclonal gammopathy of undetermined significance (MGUS) at another tertiary hospital 3 years earlier. He had been treated with systemic corticosteroids and methotrexate, but his systemic symptoms (dyspnea, dysphagia, skin swelling, and induration) had worsened over the past year, so he visited our clinic seeking further evaluation and management. The patient received high-dose intravenous immunoglobulin (IVIG) therapy once a month in combination with systemic corticosteroids. After three courses of IVIG, his cutaneous symptoms and dyspnea had improved dramatically. Herein we report a case of scleromyxedema with systemic involvement with significant improvement following IVIG therapy.