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case_images: Clinical Presentation of the Patient in the right vulva, groin, and thigh ((A): Erythema and swelling in mid-January 2021; (B) Erythema, swelling, and multiple superficial ulcers on February 18, 2021; (C) Enlargement of skin ulcers with local necrosis on March 11, 2021; (D) Further progression of skin ulcers on March 17, 2021).
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case_images: Since the day before 2 months ago, the patient had experienced itching in the right vulva with no obvious cause, followed by the development of erythema, swelling, and stiffness (Figure 1A). However, there was no significant improvement, and the skin rash progressively worsened (Figure 1B), accompanied by severe pain but no fever or chills.  The patient did not perform further examinations or treatments after discharge for her poor compliance, then the ulceration gradually expanded (Figure 1C), accompanied by severe pain. After receiving intravenous cefmetazole 1.0g twice daily for anti-inflammatory treatment for 6 days, the ulcer showed no significant improvement and the area further expanded (Figure 1D).
case_images: Pathological manifestations for the First Biopsy: Mixed inflammatory cells including plasma cells and lymphocytes infiltration in the dermis and subcutaneous fat layer, multifocal fat necrosis with neutrophil infiltration in the subcutaneous adipose tissue, ((A). 10x10; (B). 10x20; (C). 10x40).
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case_images: Further immunohistochemical analysis showed positive staining for CD138, CD38, CD20, IgG, IgG4, MUM1, Kappa and Lambda, partial positive staining for CD3, CD30, CD5, negative staining for CD56 and PAX-5, approximately 40% IgG4/IgG ratio, 35% in hot spots for Ki-67, and focal positive staining for EBER1/2 by in situ hybridization, suggesting a high possibility of IgG4-related disease (Figures 2 and 3). and the possibility of skin involvement with plasmacytoma cannot be completely ruled out, further investigation by B-cell gene rearrangement was recommended.  
case_images: Immunohistochemistry Results after the First Biopsy: CD138 (+), CD20 (small focal +), CD3 (partially +), CD30 (partially weak +), CD38 (+), CD5 (small focal +), IgG (+), IgG4 (+), IgG4/IgG ratio approximately 40%, Kappa (+), Ki-67 (+, hot spot 35%), Lambda (+), MUM1 (+), EBER1/2 in situ hybridization (small focal +).
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case_images: Further immunohistochemical analysis showed positive staining for CD138, CD38, CD20, IgG, IgG4, MUM1, Kappa and Lambda, partial positive staining for CD3, CD30, CD5, negative staining for CD56 and PAX-5, approximately 40% IgG4/IgG ratio, 35% in hot spots for Ki-67, and focal positive staining for EBER1/2 by in situ hybridization, suggesting a high possibility of IgG4-related disease (Figures 2 and 3). and the possibility of skin involvement with plasmacytoma cannot be completely ruled out, further investigation by B-cell gene rearrangement was recommended.  
case_images: First Surgical Procedure: (A) Extensive fat necrosis with local necrosis; (B) liquefied fat and fascial necrosis; (C) Excised necrotic fat tissue; (D) Debridement deep into the muscle layer.
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case_images: Three days after transferred, under general anesthesia, the patient underwent extended excision of the ulcers in the right vulva, groin, and thigh (rapid pathological examination), and wound closure with negative pressure drainage (Figure 4).
case_images: Histopathological Findings after debridement: Lobular panniculitis, fat and fascial necrosis, liquefaction, presence of neutrophils in the necrotic area ((A). 10x10; (B). 10x20; (C). 10x40).
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case_images: The postoperative pathology showed extensive fat and septal tissue necrosis, liquidation and neutrophil infiltration in the necrotic area (Figure 5).
case_images: Postoperative Recovery after Skin Grafting and debridement.
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case_images: After improvement of the infection, the patient underwent further extended debridement, skin grafting and closure with negative pressure drainage of the ulcers in vulva, groin, and thigh on the day 8 after the third surgery, through anti-infective treatment (intravenous ceftriaxone/sulbactam sodium 2.0g once daily during 13 days, and intravenous ceftazidime 2.0g twice daily during 14 days) and dressing changes, she was discharged with much improvement after a month (Figure 6).