PMC7793697_01
Clinical course of our patient. Anti-FVIII, anti-FVIII activity; aPTT, activated partial thromboplastin time; CS, corticosteroids; FVIII, coagulation factor VIII; Ig, immunoglobulin; RTX, rituximab.
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We confirmed the prolonged aPTT with normal PT and found decreased FVIII plasma levels associated with positive anti-FVIII IgG4 autoantibodies ( Table 1  and  Figure 1 ), leading to the diagnosis of AHA. Table 1  and  Figure 1 ) with other IgG subclasses within normal range. The patient was thus diagnosed with parotid and lymph node IgG4-RD according to the 2019 ACR/EULAR classification criteria. This led to a regression of parotid and lymph node enlargement, a decrease in serum IgG4 levels, a progressive correction of FVIII and aPTT values, and a suppression of anti-FVIII plasma activity ( Table 1  and  Figure 1 ). Table 1  and  Figure 1 ). The patient was started on a new course of oral corticosteroids associated with 2 infusions of rituximab 1g, which led to a sustained remission (total follow-up of 3 years after diagnosis).
Representative images of the axillary lymph node biopsy histological examination. (A) Lymph node showing reactive follicular hyperplasia. The reactive follicle comprises germinal center surrounded by a thin mantle zone. The interfollicular area contains numbers of mature plasma cells. Hematoxylin and Eosin staining x400. (B) Lymph node showing reactive follicular hyperplasia and mature plasma cells. CD79a staining. (C, D) IgG (C) and IgG4 (D) staining. Numerous IgG4+ cells are present between follicles. The IgG4+/IgG+ cell proportion is over 40%, with more than 200 IgG4+ cells per high power field.
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Figure 2 ). Further laboratory tests showed elevated serum IgG4 levels (