Continuous dermoepidermal junction IgM detected by direct immunofluorescence: a report of nine cases

Insights Into the Pathogenesis of Bullous Pemphigoid: The Role of Complement-Independent Mechanisms

Bullous pemphigoid is an autoimmune blistering disease caused by autoantibodies targeting BP180 and BP230. While deposits of IgG and/or complement along the epidermal basement membrane are typically seen suggesting complement -mediated pathogenesis, several recent lines of evidence point towards complement-independent pathways contributing to tissue damage and subepidermal blister formation. Notable pathways include macropinocytosis of IgG-BP180 complexes resulting in depletion of cellular BP180, direct induction of pro-inflammatory cytokines from keratinocytes, as well as IgE autoantibody- and eosinophil-mediated effects. We review these mechanisms which open new perspectives on novel targeted treatment modalities.

Immunoglobulin M pemphigoid

BACKGROUND

Pemphigoid diseases are a heterogeneous group of autoimmune blistering disorders characterized by predominant deposition of immunoglobulin G or immunoglobulin A autoantibodies against structural proteins of the dermoepidermal junction (DEJ). Sole linear immunoglobulin M (IgM) deposits at the DEJ in pemphigoid diseases have been observed; however, IgM-specific target antigens have not been identified.

OBJECTIVE

Characterization of patients with IgM pemphigoid.

METHODS

Skin biopsy specimens and sera from IgM-positive patients were assessed using histopathology, direct and indirect immunofluorescence microscopy, enzyme-linked immunosorbent assays, immunoblotting, cryosection assay, complement fixation test, and internalization assays.

RESULTS

Tissue-bound linear IgM deposits along the DEJ and circulating IgM autoantibodies against type XVII collagen (Col17) were detected. These circulating IgM autoantibodies showed no complement activating or blister inducing capacity, but the ability of Col17 internalization ex vivo.

LIMITATIONS

Limited number of patients.

CONCLUSION

This study provides further evidence for the role of IgM autoantibodies in pemphigoid disease and highlights Col17 as a target antigen in IgM pemphigoid.

Dermatoses of pregnancy: Nomenclature, misnomers, and myths

The most recent reclassification of dermatoses of pregnancy includes polymorphic eruption of pregnancy, atopic eruption of pregnancy, and pemphigoid gestationis; intrahepatic cholestasis of pregnancy, strictly not a dermatosis, was included in specific dermatoses of pregnancy for working purposes. Another dermatosis, pustular psoriasis of pregnancy, could be included for similar reasons. The nomenclature of these pregnancy-specific eruptions has been revised several times, generating potential confusion among practitioners. Clouding the picture further are misnomers that have been used to describe dermatoses of pregnancy. In addition, several cutaneous conditions that are associated with, but not specific to, pregnancy, have been misunderstood, which has resulted in certain myths among patients and physicians. In this contribution, we describe how the nomenclature of each dermatosis of pregnancy has evolved to fit the current classification scheme. We then identify several misnomers that have generated confusion within the scheme. Finally, we debunk several myths that have developed around cutaneous conditions outside of this scheme, in both mother and newborn.

Bullous tinea pedis with direct immunofluorescence positivity: when is a positive result not autoimmune bullous disease?

Skin biopsy for direct immunofluorescence (DIF) testing is an essential tool in the diagnosis of blistering diseases. In the majority of cases, positive epidermal immunofluorescent staining is indicative of an autoimmune bullous disease (AIBD). We identified 2 patients with bullous dermatophyte infection diagnosed on hematoxylin- and eosin-stained sections who had positive DIF findings on biopsy of perilesional skin. We subsequently reviewed the literature regarding positive DIF findings in conditions other than AIBD. Other infections, including herpesviridae, scabies, and orf, have rarely been reported to yield positive DIF findings, with positive staining at the dermoepidermal junction. Some genodermatoses and many inflammatory skin diseases, including lichen planus, psoriasis, graft-versus-host disease, among others, may also have DIF findings mimicking those of both intra- and subepidermal AIBD. Although rare, positive DIF results occur in conditions other than AIBD. In many instances, the pathophysiological mechanisms behind immunoreactant deposition in these conditions are poorly understood. Misleading DIF results may lead to delay in correct diagnosis and treatment. Clinicians should be aware of potential alternate sources of positivity when there is lack of clinical correlation with immunofluorescence findings.

Less well-defined dermatoses of pregnancy

Over the past several decades, many specific and nonspecific dermatoses of pregnancy have been described. The lack of a well-defined clinical and histological features as well as reproducibility in some of these entities has led to confusing reports in the literature. In this review article, an account of these nonspecific dermatoses of pregnancy will be presented in an attempt to shed light on their nosology and to better categorize them in view of the recent literature findings.

Dermatoses of pregnancy

The dermatoses of pregnancy can be classified into the following 3 groups: physiologic skin changes in pregnancy, dermatoses and cutaneous tumors affected by pregnancy, and specific dermatoses of pregnancy. Correct diagnosis and classification are essential for the treatment of these disorders, when necessary. Laboratory investigations are required when the diagnosis remains in question despite a careful history and thorough physical examination. A discussion with the pregnant woman about the nature of her skin condition, and the possible fetal risks associated with it, is imperative.

How reliable is the basement membrane phenomenon in the diagnosis of systemic lupus erythematosus?

BACKGROUND

Although the basement membrane (BM) phenomenon is considered a good test to differentiate between systemic (SLE) and discoid lupus erythematosus (DLE), our observations question its reliability.

METHODS

Direct immunofluorescence stain was done to detect immunoglobulins and complement deposits in 10 SLE patients and in 10 healthy controls. Specimens were taken from the normal skin of the dorsa of hands.

RESULTS

The group of SLE patients showed deposits of IgG in 4, IgM in 7, IgA in 1, C3 in 7, and C4 in 1 patient. The group of healthy controls showed IgM in 2, C3 in 5, C4 in 2 cases, but no IgG or IgA deposits.

CONCLUSION

A positive BM phenomenon test could be found in normal individuals and may be due to the effect of ultraviolet rays. We think that the BM phenomenon has a limited reliability in diagnosing SLE.