Abstract

Lichen myxedematosus (LM) is a chronic cutaneous mucinosis, which can present as localized LM or a generalized systemic form of scleromyxedema. The differential diagnosis is a clinical challenge and determined by a combination of clinical presentation, serum laboratory test, and histological examination. Although no reliable histological features distinguishing localized LM from scleromyxedema have been characterized, our recent publication suggests that the presence of groups of plasma cells, which also show light chain restriction, could be a distinct histological clue for localized LM. In this report, we provided two additional cases of localized LM and compared it to a case of scleromyxedema. Microscopic examination revealed prominent perivascular dermal infiltrate of lambda light chain-restricted plasma cells in localized LM by in situ hybridization but not in scleromyxedema. This finding is consistent with our previous publication. The absence of light chain-restricted plasmacytic component in the case of scleromyxedema reinforces this histological feature in differential diagnosis. Despite the unclear pathogenesis of LM, most literature supports the theory of fibroblast proliferation stimulated by systemic cytokines and paraproteins. However, growing evidence suggests that systemic effect cannot completely explain localized LM. The findings from this report supports our previously proposed theory that light chain-restricted plasmacytic microenvironment primarily attributes to the fibroblast proliferation in localized LM rather than systemic cytokines and paraproteins. Although further validation is required for this theory, our findings provide in-depth understanding in the pathogenesis of LM and emphasize the significance of light chain-restricted plasma cells in localized cutaneous metabolic disorder.

Financial Disclosure:
No current or relevant financial relationships exist.