A Comparative Study of Direct Immunofluorescence Patterns in Linear IgA Bullous Dermatosis Versus Dermatitis Herpetiformis

Background: Dermatitis herpetiformis (DH) is typically characterized by granular IgA deposition in the papillary dermis on direct immunofluorescence (DIF), and linear IgA bullous dermatosis (LABD) is characterized by linear deposition of IgA along the basement membrane. Other DIF findings in both conditions may include IgG, IgM, and C3 deposition in various patterns. In cases where immunofluorescence findings are unclear, such as continuous but somewhat granular IgA deposition along the dermal–epidermal junction, additional DIF patterns may be helpful in the diagnostic process. Methods: Forty-five cases of digitized images of LABD and 48 digitized images of DH cases were analyzed. The data regarding the positivity and patterns of immunoglobulins were documented and analyzed. Results: None of the LABD cases had a picket fence pattern, while 47.9% (n = 23) of the DH cases had the pattern. Elevated levels of IgG and IgM were found in LABD compared with DH. In DH, higher IgM and kappa light chain levels were observed in the deposited particles compared with those in LABD. Conclusions: The “picket fence pattern” is highly specific for DH (Specificity 100%) but less sensitive (Sensitivity 47.9%). It may be helpful to differentiate between DH and LABD for a more accurate diagnosis.