The Utility of C4d Immunohistochemistry on Formalin-Fixed Paraffin-Embedded Tissue in the Distinction of Polymorphic Eruption of Pregnancy From Pemphigoid Gestationis

Abstract

Polymorphic eruption of pregnancy (PEP), formerly known as pruritic urticarial papules and plaques of pregnancy, is a dermatosis of pregnancy that must be distinguished from pemphigoid gestationis (PG). Although this differential diagnosis may be possible on routine histology, an additional biopsy for direct immunofluorescence (DIF) is often needed. Recent studies have demonstrated the utility of anti-C4d or anti-C3d antibodies in the diagnosis of bullous pemphigoid (BP) in formalin-fixed paraffin-embedded tissue (FFPE). We investigated the utility of routine immunohistochemistry (IHC) for anti-C4d in FFPE tissue in the specific differential diagnosis of PEP versus PG in known, DIF-proven cases. We performed C4d IHC on PEP (n = 11), PG (n = 8), DIF-proven BP (n = 12), and other common dermatoses (n = 12) that are typically DIF negative. None of the PEP cases (0/11) or the other common dermatoses (0/12) demonstrated C4d positivity at the basement membrane zone. In comparison, 100% of PG cases (8/8) and 83.3% of BP cases (10/12) showed linear C4d immunoreactant deposition along the basement membrane zone. The results demonstrate the potential utility of C4d IHC in FFPE tissue for distinguishing PEP from PG, thus potentially obviating the need of a repeat biopsy for DIF, particularly in C4d-negative cases where there is a low suspicion of PG on both clinical and histological grounds. Also, patients with positive C4d-positive immunoreactivity may also potentially proceed directly to less invasive serological confirmatory testing, such as BP180 NC16a enzyme-linked immunoabsorbent assay.

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

“…The results obtained in our series with an unselected group of patients with newly diagnosed BP over a 3‐year period are hence in contrast with those from four previous studies . The latter reported sensitivities of 70–100% of IHCA when compared with DIF, as well as a high concordance of the results between IHCA and DIF.…”

“…Although DIF studies represent the gold standard for the diagnosis of BP, they often have a number of disadvantages, such as the necessity of obtaining a second biopsy, rapid transport of the sample, specialized technical processing and, finally, a relatively high cost . For these reasons, a few studies have recently assessed the value of immunohistochemistry analyses (IHCA) on paraffin‐embedded tissue as an alternative for the diagnosis of autoimmune bullous skin diseases . In other immune‐mediated diseases, such as renal diseases, IHCA already constitute a well‐established diagnostic procedure …”

Mechanisms of Disease: Pemphigus and Bullous Pemphigoid

“…In fact, if DIF is negative for C3, the diagnosis of BP is doubtful. Immunohistochemical staining of formalin-fixed biopsies for complement proteins C3 (C3d) and C4d can be used to support a diagnosis of BP in case only paraffin-embedded, and not fresh frozen, tissue is available (104, 105). Indirect immunofluorescence shows circulating IgG that binds the epidermal basement membrane in most cases (Figure 1h).…”

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

“…1,2 More recently, commercially available mouse monoclonal and rabbit polyclonal antibodies have been produced that are able to reliably detect human C3d and C4d, stable component of classic complement activation, on FFPE biopsies using immunoenzymatic techniques. The usefulness of immunohistochemical detection (IHC) of C3d and C4d in the diagnosis of inflammatory dermatoses, including AIBD, has been addressed in some studies [3][4][5][6] ; these included a limited number of biopsies or studied a variety of inflammatory dermatoses without targeting specifically AIBD, and their results were sometimes contradictory. 6 The purpose of this study was to further assess the usefulness of immunoperoxidase detection of C4d in FFPE skin specimens in the diagnosis of BP and P.…”