Immunofluorescence mapping vs. electron microscopy in epidermolysis bullosa: comparative retrospective study in 84 genetically confirmed patients

Background Epidermolysis bullosa is a rare blistering disorder caused by mutations > 21 genes. Genetic testing, particularly Next Generation Sequencing (NGS), is the current gold standard. Alternative tools such as immunofluorescence mapping (IFM) and electron microscopy (EM) aid in subclassifying EB, yet few studies have compared their performance. Objective To assess the accuracy, specificity, and sensitivity of IFM and EM, using genetic diagnosis as the reference standard. Methods Retrospective study of 84 genetically confirmed EB patients who underwent IFM and EM. Results IFM correctly diagnosed 65.5% of cases, outperforming EM (55.9%). IFM showed greater sensitivity for EBS (82.4%), JEB (100%) and RDEB (36.4%) compared with EM (60.8%, 87.5%, and 18.2%), while EM performed better in DDEB. Freshly blistered specimens, naturally occurring or correctly induced, improved accuracy for both methods, while biopsy sites (foot, arm) performed similarly. Agreement with genetics was moderate for both IFM (κ=0.434, p < 0.001) and EM (κ=0.400, p < 0.001). IFM provided the fastest results (~72 h), followed by EM (~4 weeks), whereas genetic testing required 10 weeks–6 months. Conclusions IFM is a reliable, cost-effective tool when performed with proper technique, ideally on a fresh (<12 h) blister from the foot. EM can complement IFM, due to its subtype-specific limitations, but expanding NGS access remains essential. These findings support an integrated diagnostic strategy that maximizes accuracy in routine clinical settings where genetic testing is not available.