The utility of C4d immunohistochemistry on formalin-fixed paraffin-embedded tissue in the distinction of polymorphic eruption of pregnancy from pemphigoid gestationis

Role of C4d immunohistochemical marker in the diagnosis of bullous pemphigoid: A cross-sectional study

Objective To determine the diagnostic utility of C4d immunohistochemical marker in cases of bullous pemphigoid by calculating the sensitivity, specificity, positive predictive value and negative predictive value. Methods We conducted an exploratory study (retrospectively and prospectively) from January 2017 to June 2022. All direct immunofluorescence proven cases of bullous pemphigoid were included in the study while cases with inadequate tissue for immunohistochemistry studies were excluded. Results Among the 57 cases of bullous pemphigoid, 49 showed positivity for C4d marker. All the ten control cases of inflammatory dermatoses were negative for C4d staining. A sensitivity of 86%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 55.56% were calculated with a confidence interval of 95%. Conclusion Direct immunofluorescence on fresh or frozen skin tissue remains the gold standard. But in circumstances where direct immunofluorescence facilities are not available, C4d immunohistochemistry marker staining on formalin-fixed paraffin-embedded material submitted for standard microscopic investigation can, in most cases, confirm the diagnosis of bullous pemphigoid, obviating the need for a second biopsy. Limitation It is a single centre study. Selection bias may come into play.

Is it Possible to Obtain Immunofluorescence Data in Formalin-Fixed Paraffin-Embedded Skin Samples for the Diagnosis of Pemphigus Vulgaris and Bullous Pemphigoid

OBJECTIVE

The gold-standard method for assessment of autoimmune bullous disease is direct/indirect immunofluorescence (IF) examination applied to fresh frozen tissue. Since the sensitivity of IF is greatly reduced in formalin-fixed paraffin-embedded (FFPE) tissues, IF cannot be relied upon in these samples. However, immunohistochemistry with the C4d antibody is a promising marker used as a surrogate for immune complex deposition, in nephropathology practice, and the paraffin IF method is also used as a `salvage` technique when fresh frozen tissue is not available or lacks glomeruli. We aimed to investigate whether it is possible to obtain immunofluorescence data from FFPE tissues diagnosed with bullous pemphigoid (BP) and pemphigus vulgaris (PV) and its relationship with inflammatory parameters in the skin.

MATERIAL AND METHODS

Eighty-nine in-house cases with both IgG and C3 positivity by routine immunofluorescence examination were included in the study. Inflammation parameters were evaluated in hematoxylin-eosin sections. Immunofluorescence study with IgG protease digestion and C4d immunohistochemistry were performed.

RESULTS

Results of 83 biopsies were obtained by paraffin immunofluorescence with IgG. There were positive reactions in 28 (34%) of these 83 biopsies. Five of the 28 positive results belonged to BP (18%), and 23 were PV (82%). Ten positive results were on lesional skin (36%), and 18 (64%) were on non-lesional skin. In the immunohistochemical study with C4d, 84 biopsy results were obtained. There were positive reactions in 34 (40.4%) of 84 biopsies. Of the 34 positive results, 12 belonged to BP (35.3%) and 22 to PV (64.7%). Again, 22 (64.7%) of 34 positive results belonged to lesional skin, and 12 (35.3%) belonged to non-lesional skin. When both techniques were used together, 44 (54%) of 81 biopsies yielded positive results for at least one of the two studies, while in 37 (46%), both tests showed negative results.

CONCLUSION

The sensitivity of both IgG and C4d was less than in the literature, especially in BP-diagnosed biopsies. Positive samples were mostly PV. In conclusion, obtaining immunofluorescence data in FFPE samples is possible and is independent of the related skin being lesional or not, however, negative results should not be relied upon.

Updates on the dermatopathology of pregnancy-associated skin conditions

Pathologists provide valuable input in the dermatological care of pregnant patients in various contexts. This article provides dermatopathology updates on cutaneous changes associated with pregnancy, organized based on the following classification system: physiological skin changes in pregnancy, specific dermatoses of pregnancy, dermatoses modified in pregnancy, and skin neoplasms in pregnancy. Awareness of the impact of pregnancy on the skin by pathologists is important, as this is an opportunity to contribute to diagnostic precision in this patient population.

Direct Immunofluorescence of IgG on Formalin-Fixed Paraffin-Embedded Tissue by Heat-Induced Antigen Retrieval as a Sensitive Method for the Diagnosis of Pemphigus

Purpose

Direct immunofluorescence (DIF) on frozen sections (DIF-F) plays a key role in the identification and differential diagnosis of bullous dermatoses, which are a group of critical autoimmune diseases that include pemphigus, bullous pemphigoid (BP), and epidermolysis bullosa acquisita (EBA). However, this technique requires specialized laboratory equipment conditions, sample acquisition and sample preservation. In this study, the application value of DIF on paraffin-embedded tissue sections (DIF-P) detecting IgG using heat-induced antigen retrieval (HIAR) in the diagnosis of bullous dermatosis was explored.

Patients and Methods

Samples from 12 patients with pemphigus vulgaris (PV), 10 patients with pemphigus foliaceus (PF), 17 patients with BP, and 4 patients with EBA were retrospectively studied for DIF-P IgG detection. Formalin-fixed, paraffin-embedded tissue (FFPE) was used, and the antigen retrieval method used in the experiment was HIAR. All patients were diagnosed with the autoimmune bullous disease (AIBD) based on clinical presentation, histopathology, DIF-F, and enzyme-linked immunosorbent assay (ELISA).

Results

Intercellular staining for IgG in the epidermis was successful in paraffin-embedded tissue sections in 11 of 12 PV samples and in all 10 PF samples. IgG at the basement membrane zone (BMZ) was not detected by immunofluorescent staining in 17 BP samples and 4 EBA samples.

Conclusion

The detection of IgG by DIF-P using HIAR can be used for the diagnosis of pemphigus as an alternative method to DIF-F.

Recognizing, Diagnosing, and Managing Pregnancy Dermatoses

Pregnancy dermatoses are inflammatory skin disorders that occur during pregnancy or immediately postpartum. This heterogenous group of disorders includes pemphigoid gestationis, polymorphic eruption of pregnancy, intrahepatic cholestasis of pregnancy, atopic eruption of pregnancy, and pustular psoriasis of pregnancy. In this article, we provide a comprehensive literature review of each condition focusing on nomenclature, epidemiology, pathogenesis, clinical presentation, diagnosis, differential diagnosis, maternal risk, fetal risk, and treatment. We aim to increase awareness and help clinicians recognize, diagnose, and manage these unique conditions.

Immunoglobulin and Complement Immunohistochemistry on Paraffin Sections in Autoimmune Bullous Diseases: A Systematic Review and Meta-analysis

ABSTRACT

Immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded tissue has been proposed as a potential tool in the diagnosis of autoimmune bullous diseases (AIBDs) in lieu of standard direct immunofluorescence (DIF) microscopy. To comprehensively determine the diagnostic accuracy of immunoglobulin and complement IHC for diagnosis of AIBDs, we conducted a systematic review and multivariate Bayesian model-based meta-analysis of the literature. Quality and heterogeneity assessment of studies was performed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) checklist and the I2 index, respectively. Electronic searches using PubMed from April 1964 to July 2020 identified 14 articles meeting predetermined inclusion and exclusion criteria. Median sensitivities with 95% credible intervals in pemphigus and pemphigoid were 0.24 (0.01-0.89) and 0.22 (0.02-0.77) with immunoglobulin G (IgG), 0.77 (0.39-0.95) and 0.25 (0.02-0.85) with IgG4, 0.11 (0.02-0.32) and 0.86 (0.56-0.98) with C3d, and 0.84 (0.56-0.97) and 0.75 (0.37-0.94) with C4d, respectively. Specificities were 1.00 (0.00-1.00) with IgG, 0.98 (0.89-1.00) with IgG4, 0.99 (0.97-1.00) with C3d, and 0.99 (0.97-1.00) with C4d. The risk of bias and heterogeneity among studies was a serious problem, decreasing the level of evidence. Our work suggests that, in selected cases, paraffin-based IHC may be a helpful procedure to screen for AIBDs, especially when specialized laboratories and/or biopsy specimens for DIF do not exist. Nevertheless, more studies with a refined quality design are needed to explore the true usefulness of this diagnostic method in AIBDs.

Advances in the diagnosis of autoimmune bullous dermatoses

Autoimmune bullous dermatoses are defined by autoantibodies directed against adhesion proteins in the epidermis or basement membrane zone, resulting in blister formation on the skin and mucosa. Diagnosis depends on lesional biopsy for histopathology and perilesional biopsy for direct immunofluorescence. Additional diagnostic methods include indirect immunofluorescence, enzyme-linked immunosorbent assay, and immunoblot (Western blot), which may be selected in specific clinical scenarios due to improved sensitivity and/or specificity. This contribution reviews the available evidence supporting the use of each method to provide a practical reference for clinicians when diagnosing autoimmune bullous disorders. Techniques and cost are reviewed, and newer diagnostic techniques with potential for clinical application are.

Immunological methods for the diagnosis of oral mucosal diseases

Immunological methods, which have been widely used in autoimmune blistering diseases (AIBDs) of the oral mucosa, can also be adopted as auxiliary diagnostic tools in oral lichen planus (OLP) and discoid lupus erythematosus (DLE). AIBDs, characterized by autoantibodies against structural proteins of keratinocytes or the basement membrane zone, clinically present as blisters and erosions of the oral mucosa. When atypical lesions occur, OLP or DLE may be confused with AIBDs. The improvement of diagnostic accuracy is necessary due to the significant differences in treatment and prognosis among these diseases. A variety of immunological methods are used for qualitative and quantitative detection of target antigens and autoantibodies. These methods can evaluate efficacy of treatment, monitor diseases and guide treatment decisions. In this review, we discuss the application of immunofluorescence, biochemical tests, and protein microarrays for AIBDs, OLP and DLE, as well as the differential diagnostic methods using immunological tests.

Specific dermatoses of pregnancy other than pemphigoid gestationis

Specific dermatoses of pregnancy are skin disorders that occur specifically during or immediately after pregnancy and cannot be found in non-pregnant patients. According to the current consensus, they include atopic eruption of pregnancy (AEP), polymorphic eruption of pregnancy (PEP), pemphigoid gestationis (PG), and intrahepatic cholestasis of pregnancy (ICP). The diagnosis of specific dermatoses of pregnancy can be challenging due to their variation in clinical presentation; moreover, the tests currently available do not always provide the clue for the diagnosis. However, some distinctive features may be helpful to differentiate between such entities. Accordingly, the knowledge of specific dermatoses of pregnancy and of their management is critical, since their early recognition may allow to provide care for the mother and prevent potential increased fetal risk. In fact, while AEP and PEP do not affect maternal and fetal prognosis, PG and, mainly, ICP are associated to maternal complications as well as the risk of fetal loss. In this paper, the epidemiology, pathogenesis, clinical features as well as management of AEP and PEP are reviewed in detail, while PG is described in another article of this issue. Moreover, the main features of ICP, which cannot be considered a primarily skin disease but may be managed first by dermatologists, are reported.

Pemphigoid gestationis: current perspectives

Many skin diseases can occur in pregnant women. However, a few pruritic dermatological conditions are unique to pregnancy, including pemphigoid gestationis (PG). As PG is associated with severe morbidity for pregnant women and carries fetal risks, it is important for the clinician to quickly recognize this disease and refer it for dermatological evaluation and treatment. Herein, we review the pathogenesis, clinical characteristics, and management of PG.

Polymorphic eruption of pregnancy: Review of literature

Polymorphic Eruption of Pregnancy (PEP) is one of the most common dermatosis related to pregnancy. PEP usually consists of pruritic papules and plaques appearing in the third trimester of pregnancy. It is more common in primigravidae and twin pregnancies. Although not associated with poorer foetal or maternal outcomes, it may be hard for pregnant women to endure. The diagnosis is easy if suspected, though sometimes it may be hard to distinguish from other dermatosis such as atopic eczema of pregnancy, pemphigoid gestationis or dermatitis. Topical treatment with emollients and low-medium potency steroids is usually effective but systemic steroid treatment may be required. PEP is self-limiting and resolves days or weeks after the first appearance or after delivery. In this article, the authors aim to review the literature published from 2000 onwards regarding the subject, either in English or Portuguese.

Application of C4d Immunohistochemistry on Routinely Processed Tissue Sections for the Diagnosis of Autoimmune Bullous Dermatoses

The diagnosis of autoimmune bullous dermatoses relies greatly on direct immunofluorescence (DIF) examination performed on frozen tissue sections, showing deposits of immunoglobulins and/or C3 on specific cutaneous structures. However, frozen material is not always available for DIF; therefore, alternative techniques are needed in the diagnostic procedure. We therefore tested the usefulness of C4d immunohistochemistry on formalin-fixed, paraffin-embedded tissue sections for the diagnosis of bullous pemphigoid (BP) and pemphigus (P). A retrospective immunohistochemical study was performed on biopsies of BP (n: 29) and P (n: 22, including 19 Pemphigus vulgaris and 3 paraneoplastic), submitted for routine histological examination and compared with DIF on the corresponding frozen sections. Twenty-five BP biopsies (86.2%) showed C4d deposits seen as a linear labeling along the dermal-epidermal junction and on the membrane of basal keratinocytes. Seventeen P biopsies (77.2%) showed C4d deposits in a classical "intercellular" pattern, predominating on the lower epidermal layers. The sensitivity, specificity, positive predictive value, and negative predictive value reached 86%, 98%, 96%, and 92% in BP, respectively and 77%, 98%, 94%, and 92% in P, respectively. Furthermore, in the cases where serological tests were available, the sensitivity of C4d detection was higher than that of enzyme-linked immunosorbent assay/indirect immunofluorescence in both BP (87% vs. 67%) and P (82% vs. 54.5%). We conclude that DIF on frozen sections still remains the gold standard for the immunopathological diagnosis of BP and P; however, in the absence of frozen material, C4d immunohistochemistry performed on routinely processed biopsy material can be of considerable help in confirming the diagnosis.

Diagnostic value of immunohistochemistry on formalin-fixed, paraffin-embedded skin biopsy specimens for bullous pemphigoid

BACKGROUND

Direct immunofluorescence microscopy (DIF) studies constitute the gold standard for diagnosis of bullous pemphigoid (BP) but depend on the availability of specialized laboratories and often on an additional skin biopsy specimen.

OBJECTIVES

To assess the value of immunohistochemical analyses (IHCA) in the diagnosis of BP using formalin-fixed, paraffin-embedded skin biopsy specimens as an alternative to DIF; and to study the correlation between the results of IHCA and the presence of histological subepidermal blister formation and of circulating autoantibodies by indirect immunofluorescence studies using split skin or by enzyme-linked immunosorbent assays.

METHODS

We included all patients newly diagnosed with BP evaluated between 2008 and 2010. There were 51 consecutive skin biopsy specimens obtained from 38 patients with BP with positive DIF.

RESULTS

By IHCA, deposits of immunoreactants were found in 45% of all tested cases. Deposits of C3d, IgG, IgM, IgE and IgA were found in 37%, 23%, 2%, 0% and 0% of cases, respectively. Deposits of C3d and/or IgG were found in 79% of the 24 cases with a blister and in 83% of the 12 cases with subepidermal blistering and positive immunoserological analyses, respectively.

CONCLUSIONS

In contrast to previous studies, our findings in an unselected patient cohort indicate that IHCA are not sufficiently sensitive to replace DIF studies for confirming the diagnosis of BP. IHCA sensitivity significantly increases in the presence of histological blistering and/or of circulating autoantibodies. IHCA represents a potential rescue diagnostic technique only if specialized laboratories and/or a second biopsy specimen for DIF are unavailable.

Mechanisms of Disease: Pemphigus and Bullous Pemphigoid

Pemphigus and bullous pemphigoid are autoantibody-mediated blistering skin diseases. In pemphigus, keratinocytes in epidermis and mucous membranes lose cell-cell adhesion, and in pemphigoid, the basal keratinocytes lose adhesion to the basement membrane. Pemphigus lesions are mediated directly by the autoantibodies, whereas the autoantibodies in pemphigoid fix complement and mediate inflammation. In both diseases, the autoantigens have been cloned and characterized; pemphigus antigens are desmogleins (cell adhesion molecules in desmosomes), and pemphigoid antigens are found in hemidesmosomes (which mediate adhesion to the basement membrane). This knowledge has enabled diagnostic testing for these diseases by enzyme-linked immunosorbent assays and dissection of various pathophysiological mechanisms, including direct inhibition of cell adhesion, antibody-induced internalization of antigen, and cell signaling. Understanding these mechanisms of disease has led to rational targeted therapeutic strategies.

Skin disease in pregnancy

Skin manifestations during pregnancy are common and diversified. This review will focus on the most important entities to be recognized by obstetricians. These are, on the one hand, physiological changes, where unnecessary investigations should be avoided, and on the other, the specific dermatoses of pregnancy. These develop electively in pregnancy, and they are currently grouped into three disorders: polymorphic eruption of pregnancy, atopic eczema of pregnancy, and pemphigoid gestationis. Arguments for recognition of these are presented including detection of anti-BP180 antibodies. Follow-up and treatment depend on the precise diagnosis. Risks in fetal prognosis may occur in rare pemphigoid gestationis cases.