Abstract

A 74-year-old woman with a diffuse skin changes including hyperpigmentation and sclerosis, consistent with a lichen sclerosus/morphea overlap syndrome, presented with a newly identified IgG/lambda monoclonal gammopathy (IgG1 M-spike 1.14 g/dl). A peri-umbilical fat pad punch biopsy was performed to rule out amyloidosis. Light microscopy of the specimen revealed papillary dermal fibrosis and dermal deposition of a congo-red-negative eosinophilic material, without epidermal changes. Immunofluorescence studies demonstrated diffuse, coarse, granular staining of the upper dermis for IgG1/lambda monoclonal immunoglobulin, as well as fine granular lace-like staining of IgG1/lambda in the intercellular spaces of the basal layers of the keratinocytes. Linear staining of the basement membrane or deposition of C3 or C1q were absent. The epidermal deposition pattern mimicked the immunofluorescence staining pattern seen in pemphigus vulgaris. Electron microscopy revealed tiny, finely stippled electron-dense aggregates with fine filamentous extensions intercalating between collagen bundles in the dermis. The epidermis exhibited subepidermal micro-blisters in areas lacking a lamina densa, with focal widening of intercellular spaces, loss of desmosomes, and associated amorphous densities. It was thus suggested that the patient’s monoclonal IgG1/lambda may have specificity for an antigenic constituent of the desmosome. The patient was thus concluded to have a “monoclonal gammopathy of dermatopathic significance,” a monoclonal IgG/lambda demonstrating binding capacity for desmosomes, but with limited amyloidogenic potential. Candidates for the antigenic target included desmoglein 1, desmoglein 3, envoplakin, periplakin, plectin, and gamma-catenin. This epidermal pattern coupled with the dermal deposition is a previously unreported pattern, and enhances our understanding of the spectrum of monoclonal gammopathy-related deposition diseases.

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