Targeting Collagen VII Antibodies in Bullous Diseases Using Efgartigimod IV (VYVGART)

Inclusion Criteria: * For DEB patients (aged 12 years or older): DEB confirmed with mutation analysis and correlated by phenotype, and treatment of at least 1 wound treated with topical gene therapy (VYJUVEK). Presence of C7 antibodies above normal cutoff on ELISA. * For (classic) EBA patients (aged 18 years or older): EBA confirmed with positive histopathology (DIF), C7 antibodies above normal cutoff on ELISA, and having at least 1 skin lesion. * The participant has a Karnofsky performance status of at least 60% at screening. * Contraceptive use by reproductive male and female patients should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies and: 1. Male participants: \- Must agree to use an acceptable method of contraception and not donate sperm from the time that the ICF is signed until they have received their last dose of IMP. 2. Female participants: * Women of childbearing potential must have a negative serum pregnancy test at screening and a negative urine pregnancy test at week 1 / baseline before study intervention can be administered. Subsequent urine pregnancy tests are to be completed at week 6, week 11, week 16, week 21, and week 26 / EoS. * WOCBP must agree to use a highly effective or acceptable contraception method until at least 90 days after they receive their last dose of IMP. Exclusion Criteria: * Linear IgA dermatosis-like EBA or other autoimmune blistering diseases (including but not limited to pemphigus vulgaris, bullous pemphigoid, mucous membrane pemphigoid). * Use of the following EBA treatments: * sulfasalazine, IVIg, subcutaneous administration of immunoglobulin (SCIg), immunoadsorption or plasma exchange within 2 weeks of the screening visit, tetracyclines with or without nicotinamide at doses higher than the recommended daily allowance (RDA)/dietary reference intake (DRI) within 2 weeks of the screening visit. * any monoclonal antibody (including rituximab or another anti-CD20 biologic) within 6 months of the screening visit. * complementary therapies-such as traditional Chinese medicines, herbs, or procedures (e.g., acupuncture)-within 4 weeks (or 5 half-lives) of the screening visit, if the investigator determines that such therapies may interfere with the study's efficacy assessments and/or potentially risk the safety of the participant. * The use of the following EBA treatments is permitted throughout the study: OCS, topical corticosteroids, conventional immunosuppressants (e.g., azathioprine, cyclophosphamide, methotrexate, mycophenolate, or mofetil), and dapsone. * Moderate to severe renal insufficiency. * Known contraindication to OCS therapy. * Clinically significant uncontrolled active or chronic, bacterial, viral, or fungal infection at screening * Medical instability limiting ability to travel to the Investigative Center * Diseases or conditions that could interfere with the assessment of safety and efficacy of the study treatment and compliance of the subject with study visits/procedures, as determined by the investigator. * Subjects actively receiving chemotherapy or immunotherapy at screening * Active drug or alcohol addiction as determined by the investigator. * Pregnant or nursing women * History of malignancy unless deemed cured by adequate treatment with no evidence of recurrence for ≥3 years before the first administration of the IMP. Participants with the following cancers can be included at any time, provided they are adequately treated prior to screening: 1. Basal cell or squamous cell skin cancer 2. Carcinoma in situ of the cervix 3. Carcinoma in situ of the breast 4. Incidental histological finding of prostate cancer (TNM stage T1a or T1b)