Multiple myeloma and congestive heart failure developed in a patient with long-standing scleredema adultorum. Staining of the myocardium, performed after her death, was positive for acid mucopolysaccharide and negative for amyloid. To the best of our knowledge, this is the first case in which acid mucopolysaccharide has been demonstrated in the myocardium, thus explaining the cardiomyopathy of scleredema adultorum. Review of the world literature enabled us to identify a statistically significant increased prevalence of plasma cell dyscrasia among patients with protracted scleredema. In all patients, plasma cell dyscrasia appeared years after the onset of scleredema. Immunofluorescent studies were negative for immunoglobulin deposition. We assume, therefore, that the plasma cell dyscrasia was secondary to scleredema.