Development and multicenter international validation of a diagnostic tool to differentiate between pemphigoid gestationis and polymorphic eruption of pregnancy

Background: Pemphigoid gestationis (PG) and polymorphic eruption of pregnancy (PEP) may be similar morphologically but confer different maternal and fetal risks. Direct immunofluorescence is the gold standard test used to differentiate between the 2 diagnoses but is not always available. Objective: To develop and validate a clinical scoring system to differentiate PG from PEP. Methods: After developing a scoring system based on differentiating clinical factors reported in existing literature, we tested its diagnostic accuracy in a retrospective international multicenter validation study in collaboration with the European Academy of Dermatology and Venereology's Skin Diseases in Pregnancy Taskforce. Results: Nineteen pregnancies (16 patients) affected by PG and 39 pregnancies (39 patients) affected by PEP met inclusion criteria. PG had a mean score of 4.6 (SD, 2.5) and PEP had a mean score of −0.3 (SD, 2.0). The area under the curve was 0.93 (95% CI, 0.86-1.00). Univariate analysis revealed that almost all criteria used in the scoring system were significantly different between the groups (P < .05), except for skip pregnancy and multiple gestations, which were then removed from the final scoring system. Limitations: Small retrospective study. Conclusion: The Pregnancy Dermatoses Clinical Scoring System may be useful to differentiate PG from PEP in resource-limited settings.