Direct immunofluorescence in the clinic for pemphigus and pemphigoid disorders.

INTRODUCTION: Direct immunofluorescence (DIF) is a cornerstone diagnostic tool for autoimmune bullous diseases (AIBDs), providing critical tissue-based visualization of immune deposits. AREA COVERED: Literatures were searched using Pubmed with DIF and pemphigus or pemphigoid or AIBD as keywords before 20 December 2025. This review details role of DIF in the diagnoses of AIBDs, both pemphigus and pemphigoid diseases, highlighting characteristic staining patterns. Pemphigus diseases show IgG/IgA/C3 depositions to keratinocyte cell surfaces, while pemphigoid diseases exhibit linear/granular basement membrane zone depositions of various immunoglobulins and complement components. DIF results are usually consistent with H&E pathological results, intraepidermal blisters for pemphigus diseases and subepidermal blisters for pemphigoid diseases. DIF findings are distinct in some subtypes of AIBDs, guiding differential diagnosis and complementing serological assays, such as indirect immunofluorescence, enzyme-linked immunosorbent assays and immunoblotting. EXPERT OPINION: DIF remains the diagnostic gold standard for AIBDs, providing indispensable tissue-specific insights, that cannot be fully replaced by serological tests. However, serological tests are more important in monitoring disease activity. Thus, when biopsy is impractical, optimal diagnosis requires synergistic use of both DIF and serological tests.