case_images: PMC10926194_01
case_images: (A) Painful, erythematous skin rash at the insulin pump injection site on the upper abdomen, just prior to presentation. (B) Area of induration at previous insulin injection site on admission, with evolving erythema, ecchymosis, and petechiae. (C) H&E staining demonstrating subcutaneous granulomatous infiltrate with numerous eosinophils. (D) 10.5x magnification showing granuloma and eosinophils. (E) Superficial and deep perivascular and interstitial infiltrate, including lymphocytes and numerous eosinophils. (F) Direct immunofluorescence with C3 deposition in dermal papillae and basement membrane. H&E, hematoxylin and eosin stain.
case_images: falgy-05-1357901-g001.jpg
case_images: PMC10926194_01_falgy-05-1357901-g001.jpg
case_images: F1
case_images: Her physical examination revealed tender, erythematous subcutaneous nodules on the bilateral flanks, lower abdomen, and arms at insulin injection sites (Figures 1A,B). Skin biopsies showed mixed dermal infiltrates with prominent lymphocytes and eosinophils and granulomatous subcutaneous infiltrate (Figures 1C-E). Direct immunofluorescence (DIF) showed patchy deposition of C3 in a granular pattern in the superficial dermal papillae with negative IgM and IgG (Figure 1F).
case_images: Timeline of the case report of insulin-induced type III HSR and co-existing insulin resistance, illustrating the changes in anti-insulin IgG autoantibody titers, treatment interventions, and the evolution of symptoms over time. HSR, hypersensitivity reaction; IgG, immunoglobulin G; IVIG, intravenous immunoglobulin; MTX, methotrexate; SC, subcutaneous; TPE, therapeutic plasma exchange.
case_images: falgy-05-1357901-g002.jpg
case_images: PMC10926194_01_falgy-05-1357901-g002.jpg
case_images: F2
case_images: Furthermore, laboratories were notable for anti-insulin IgE <0.10 kUA/L and elevated anti-insulin IgG of 27.8 U/ml, subsequently rising to >50 U/ml (Figure 2). TPE, anti-insulin IgG titer significantly declined, from >50 U/ml to 2.7 U/ml (Figure 2). Treatment was then followed with one dose of rituximab, with a planned second dose two weeks later, and the initiation of mycophenolate mofetil (MMF) for long-term immunosuppression.