Primary localized cutaneous lichen myxedematosus with light chain‐restricted plasma cells: A distinct variant of the localized form of lichen myxedematosus

Abstract

Lichen myxedematosus (LM) is a chronic cutaneous mucinosis that can present as a localized skin lesion or as a generalized systemic disease termed scleromyxedema. The differential diagnosis is determined by a combination of clinical presentation, serological studies, and histopathological examination. Currently, well‐established and accepted histopathological features to distinguish localized LM from scleromyxedema have not been elucidated. Our recent publication, together with a retrospective literature review, suggests that the presence of groups of light chain‐restricted plasma cells represents a distinct histopathological clue for the diagnosis of localized LM. In this report, we provide two additional cases of localized LM with lambda light chain‐restricted plasma cells, together with clinical and histopathological findings that are similar to our previous publication. These cases support our theory that the light chain‐restricted plasmacytic microenvironment is primarily attributed to the pathogenesis of localized LM. Therefore, we consider these cases to constitute a clinically and pathologically new variant of localized LM and name it primary localized cutaneous LM with light chain‐restricted plasma cells.