Cutaneous light chain amyloidosis and erythema elevatum diutinum as the presenting features of IgA monoclonal gammopathy: a rare case report and comprehensive literature review.

Monoclonal gammopathy (MG) associated with dermatological disorders, which is classified as monoclonal gammopathy of clinical significance (MGCS), represents a well-established complication. These dermatologic conditions are linked to the infiltration and proliferation of malignant plasma cells or the deposition of monoclonal immunoglobulin in nonmalignant monoclonal gammopathy. Immunoglobulin light chain amyloidosis (AL amyloidosis) is a clonal, non-proliferative plasma cell disorder characterized by the deposition of fragments of immunoglobulin light chains in tissues. Erythema elevatum diutinum (EED) is clearly associated with monoclonal gammopathy, particularly IgA monoclonal gammopathy, although the pathomechanism has not been clearly established. In this article, we report an extremely rare case involving the coexistence of cutaneous light chain amyloidosis (AL amyloidosis) and erythema elevatum diutinum (EED) as the presenting features of IgA monoclonal gammopathy, which to our knowledge is the first reported case. During a 5-year follow-up period, intermittent occurrence of skin lesions persisted without significant changes observed in blood system examinations. Furthermore, we provided a comprehensive review of the existing literature on EED associated with IgA MG to enhance the understanding of skin significance of MG.