F8 and immunoglobulin G4-related sclerosing disease: In our patient, both diseases were diagnosed according to standard-of-care recommendations: the patient met the clinical, serological and histological items of the ACR/EULAR 2019 classification criteria for IgG4-RD (7); and the presence of a FVIII inhibitor demonstrated by a gold-standard technique (Bethesda assay) associated with low FVIII titers confirmed AHA diagnosis (3).