EXAMINATION OF CUTANEOUS MACROGLOBULINOSIS BY IMMUNOELECTRON MICROSCOPY

Cutaneous macroglobulinosis is a rare cutaneous manifestation of Walde nstrom's disease, Lesions are thought to result from accumulation of m acroglobulin in the dermis and are therefore called IgM storage papule s. Ultrastructural findings in the previously reported cases were cont radictory and the nature of the deposits was not established by electr on microscopy, The purpose of this study was to analyse such deposits by the use of immunoelectron microscopy. A 60-year-old woman had multi ple erythematous papules for 1 year. The histopathological changes con sisted of plasmocytic infiltration of the dermis and eosinophilic depo sits, The skin changes and other investigations led to a diagnosis of Waldenstrom's disease, Samples from normal and diseased skin were anal ysed by electron microscopy and by immunogold labelling with anti-IgM antibodies, after Lowicryl K4M embedding, An extracellular electron de nse granular and filamentous material was observed in the mid- and upp er dermis, between and within the collagen bundles, No periodicity was noted and no deposits were seen at the dermoepidermal junction. Immun oelectron microscopy showed a positive labelling located only on these deposits, in both normal-appearing skin and in lesions, In this patie nt, immunoelectron microscopy clearly demonstrated the presence of lar ge amounts of IgM in the dermis, which were found in the lesions of cu taneous macroglobulinosis and in normal skin. These results suggest th at the IgM storage papules result from a greater density of deposits r ather than a site-specific accumulation.