The Value of Type IV Collagen Immunohistochemical Staining in the Differential Diagnosis of Autoimmune Subepidermal Bullous Diseases

Autoimmune subepidermal bullous diseases (AISBDs) exhibit various clinical presentations, histological appearances, prognoses, and responses to treatment. Many diagnostic techniques, such as direct immunofluorescence (IF), indirect salt-split skin IF, and enzyme-linked immunosorbent assays, are used in the differential diagnoses of AISBDs. However, these techniques require fresh frozen tissue, expensive laboratory equipment, and sophisticated laboratory techniques. The purpose of this study was to evaluate the value of type IV collagen immunohistochemical (IHC) staining for the differential diagnosis of AISBDs. Paraffin-embedded blocks of skin biopsies were selected from 28 patients with autoimmune subepidermal bullous diseases. Among these 28 cases, 24 patients exhibited bullous pemphigoid (BP), 2 exhibited epidermolysis bullosa acquisita (EBA), 1 exhibited linear immunoglobulin A dermatosis (LAD), and 1 exhibited bullous systemic lupus erythematosus (BSLE). Sections were stained for type IV collagen and examined to determine the location of type IV collagen in the subepidermal blister. Type IV collagen positivity was observed on the base of the subepidermal blister in patients with BP (24 of 24 cases) and LAD (1 of 1 case). Staining was observed on the roof of the blister in patients with EBA (2 of 2 cases) and BSLE (1 of 1 case), and irregular staining was also observed on the base in patients with EBA. In conclusion, type IV collagen IHC staining is a simple and useful diagnostic technique for the differential diagnosis of AISBDs.