Supplementary Material for: Characterization of Cutaneous Plasmacytosis at Different Disease Stages

Background/Aims: Cutaneous plasmacytosis is rare and still not well understood. A retrospective study was made of 9 Chinese patients with 1- to 15-year histories of biopsy-proven cutaneous plasmacytosis diagnosed between 2003 and 2015. Methods: Patient records and archival photographs helped establish the pattern and duration of skin lesions, and skin biopsy specimens provided additional data. Results: The mean age at diagnosis was 46.4 years. Two patients had lesions within 1 year of developing the disease, and 4 had lesions lasting longer than 5 years. One patient had lymphadenopathy of the neck that was later determined to be Castleman disease. Three patients had elevated IgG4 levels; only 2 had increased IgG4+ cells in skin tissues. Flexural accentuation was prominent. Four patients had elevated IgG levels, and 1, with an IgG level >5,000 mg/dL, developed systemic plasmacytosis (later confirmed as Castleman disease). The level of IgG4 subclass was related to disease duration, whereas IgG4+ plasma cells in tissues seemed irrelevant. Conclusion: Routine laboratory tests, especially measurement of IgG4 levels, may be useful for following patients with cutaneous plasmacytosis. Because of the retrospective nature of our study, we could only evaluate the results of a single IgG4 test for each patient, but the results pointed to cutaneous plasmacytosis in all 9 patients, who had different stages of the disease. Serial skin biopsies may also be helpful for gauging disease progress. Although IgG4-related disease was not established in any of these patients, long-term follow-up is warranted for all patients.