Direct immunofluorescence to diagnose mucous membrane pemphigoid: A retrospective study

OBJECTIVES Mucous membrane pemphigoid (MMP) is a group of rare acquired and autoimmune disorders charac-terized by the presence of autoanti-bodies against the epithelial-connective tissue junction that cause epithelial detachment and sub-epi-thelial blister formation. Direct im-munofluorescence (DIF) is the piv-otal exam for diagnosing MMP. The main objective of this retrospective study was to evaluate, in a group of patients affected by PMM, whether the multiple sample biopsy has a higher probability to obtain a positive DIF result compared to the single sample biopsy. MATERIALS AND METHODS Clinical records of patients affected by MMP and treated at the Unit of Oral Medicine and Oral Laser Surgery Unit of Parma University from 2000 and 2018 were retrieved. Inclusion criteria were:-presence of desquamative gingi-vitis and/or oral mucosa erosions, ulcers, blisters or scars with or without extra-oral involvement;-DIF exam demonstrating a linear deposition of IgG, IgA, or C3 along the epithelial basement membrane zone. The medical records of the patients included were reviewed and for each patient demographic and clinical data and those relating to the diagnostic investigations carried out were collected. For the samples subjected to the DIF test, the following were recorded: the location of the sample, whether the sample was single or multiple and the result of the analysis. RESULTS Nineteen patients were included, 10 females (53.6%) and 9 (47.4%) males which ages ranged from 39.9 to 84.2 years (mean = 66.1±13 years). A total of 30 spec-imens were submitted to DIF analysis and 21 resulted positive (70%). IgG, IgA and C3 deposits were observed in 71.4%, 28.6% and 76.1% of positive specimens, re-spectively. No correlation was found regarding test positivity and sampling site. In 12 interventions a single sample was collected and 9 resulted positive (75%). In 9 interventions 2 samples were collected and at least 1 specimen resulted positive in all the cases (100%). Three patients, who were initially DIF negative showed persistent le-sions, so they repeated the exam which then resulted positive. CONCLUSIONS Data from our patient cohort sug-gest that DIF is associated with a high percentage of false-negative results (30%), thus a negative DIF test does not exclude the MMP di-agnosis. Multiple and repeated sampling can enhance the chanc-es of diagnosis confirmation. CLINICAL SIGNIFICANCE Mucous membrane pemphigoid, although rare, is an important dis-order for the associated morbidity, and, exceptionally, mortality. An early correct diagnosis, based on clinical and laboratory data, is the first step for effective manage-ment of the affected patients. The direct immunofluorescence exam is mandatory for confirming the diagnosis but it shows some critical issues. Multiple and repeated biopsies are useful to reduce the number of missed diagnoses.