State-of-the-art diagnosis of autoimmune blistering diseases.

Autoimmune blistering disorders (AIBDs) are a heterogeneous group of approximately a dozen entities comprising pemphigus and pemphigoid disorders and dermatitis herpetiformis. The exact diagnosis of AIBDs is critical for both prognosis and treatment and is based on the clinical appearance combined with the detection of tissue-bound and circulating autoantibodies. While blisters and erosions on the skin and/or inspectable mucosal surfaces are typical, lesions may be highly variable with erythematous, urticarial, prurigo-like, or eczematous manifestations. While direct immunofluorescence microscopy (IFM) of a perilesional biopsy is still the diagnostic gold standard, the molecular identification of the major target antigens opened novel therapeutic avenues. At present, most AIBDs can be diagnosed by the detection of autoantigen-specific serum antibodies by enzyme-linked immunosorbent assay (ELISA) or indirect IFM when the clinical picture is known. This is achieved by easily available and highly specific and sensitive assays employing recombinant immunodominant fragments of the major target antigens, i.e., desmoglein 1 (for pemphigus foliaceus), desmoglein 3 (for pemphigus vulgaris), envoplakin (for paraneoplastic pemphigus), BP180/type XVII collagen (for bullous pemphigoid, pemphigoid gestationis, and mucous membrane pemphigoid), laminin 332 (for mucous membrane pemphigoid), laminin ß4 (for anti-p200 pemphigoid), type VII collagen (for epidermolysis bullosa acquisita and mucous membrane pemphigoid), and transglutaminase 3 (for dermatitis herpetiformis). Indirect IFM on tissue substrates and in-house ELISA and immunoblot tests are required to detect autoantibodies in some AIBD patients including those with linear IgA disease. Here, a straightforward modern approach to diagnosing AIBDs is presented including diagnostic criteria according to national and international guidelines supplemented by long-term in-house expertise.

Classification and Antigen Molecules of Autoimmune Bullous Diseases.

Autoimmune bullous diseases (AIBDs), which are a group of tissue-specific autoimmune diseases of the skin, present with various blistering lesions on the skin and mucous membranes, and show autoantibodies of IgG, IgA and IgM against epidermal cell surfaces and basement membrane zone. To date, AIBDs have been classified into a number of distinct subtypes by clinical and histopathological findings, and immunological characteristics. In addition, various biochemical and molecular biological studies have identified various novel autoantigens in AIBDs, which has resulted in proposals of new subtypes of AIBDs. In this article, we summarized various distinct AIBDs, and proposed the latest and most comprehensive classification of AIBDs with their autoantigen molecules.

Pathophysiology of Generalized Pustular Psoriasis.

Generalized pustular psoriasis (GPP) is a rare, severe form of pustular psoriasis characterized by widespread, recurrent episodes of neutrophil-rich pustule formation in the epidermis, which can be accompanied by fever and systemic inflammation. Recent clinical, histologic, and genetic evidence indicates that GPP is a distinct entity from plaque psoriasis, with different cytokine pathways predominant in the manifestation of each disease. The interleukin-36 (IL-36) signaling cascade plays a key role in regulating the innate immune system, and its dysregulation appears central to the pathogenesis of GPP. The altered expression of various IL-36 pathway constituents has been shown to cause a positive feedback loop of uncontrolled signaling and excess production of inflammatory cytokines, which in turn leads to chemokine induction and neutrophil recruitment in the epidermis. Given the potentially life-threatening nature of GPP episodes, drug interventions that rapidly achieve disease resolution are required. Early phase data indicate that treatments targeting various components of the IL-36 inflammatory cascade represent promising areas of research. However, there are currently no therapeutic agents specifically approved for GPP in the USA or Europe. Understanding the inflammatory pathways, associated risk factors, and role of neutrophils in the manifestation and perpetuation of GPP flares remains a key goal in developing effective therapeutics. In this article, we summarize the current understanding of GPP, describe novel therapeutic opportunities, and detail how the unique pathophysiology of the disease may inform future treatment strategies.

The human microbiome in immunobullous disorders and lichen planus.

For several decades, there has been a significant growth in the incidence of autoimmune diseases. Studies indicate that genetic factors may not be the only trigger for disease development and that dysbiosis of the microbiome may be another mechanism involved in the pathogenesis of autoimmune diseases. The role of the microbiome in the development of common skin disorders such as psoriasis, atopic dermatitis, acne and rosacea is increasingly well understood. However, few studies have focused on lichen planus and the rare acquired immunobullous diseases, both mucocutaneous groups of disorders linked to skin, oral and gut microbiomes. This review provides an insight into the current understanding of how the microbiome may contribute to the development of autoimmunity and to the maintenance and exacerbation of acquired immunobullous and lichenoid diseases. These mechanisms may have implications for future preventive and therapeutic approaches.

Impact of adding an IgG4 conjugate to routine direct immunofluorescence testing for subepithelial and intraepithelial autoimmune blistering disorders.

BACKGROUND: Certain autoimmune bullous dermatoses are mediated by autoantibodies of the IgG4 subclass. We determined the diagnostic impact of adding IgG4 to our conventional direct immunofluorescence (DIF) panel. METHODS: For all cases submitted to our referral laboratory for DIF over 1 month (n = 630), we performed IgG4 testing and collected consecutive biopsy specimens showing definite or indeterminate linear or cell-surface deposition of IgG, IgG4, and/or C3. On retrospective blinded review, we classified the pattern and whether the findings were definite, indeterminate, or negative. When present, substantial background staining was recorded. RESULTS: Seventy DIF specimens met the inclusion criteria. Of 22 (31.4%) specimens equivocal for linear or cell-surface deposition, 9 (40.9%) had definitive IgG4 findings, either linear (3 of 14 equivocal linear cases; 21.4%) or cell-surface (6 of 8 equivocal cell-surface cases; 75.0%). Background deposition was substantial in 14 cases (20.0%) for IgG but in none for C3 or IgG4. CONCLUSION: IgG4 allowed the classification of over 40% of DIF cases that were otherwise equivocal by IgG and C3. IgG4 staining showed lower levels of non-specific background staining than IgG or C3. IgG4 appears to contribute most value in cases with cell-surface deposition or with equivocal linear IgG deposition and negative C3 results.

Targeting heat shock proteins 90 and 70: A promising remedy for both autoimmune bullous diseases and COVID-19.

Heat shock proteins (Hsps), including Hsp90 and Hsp70, are intra- and extracellular molecules implicated in cellular homeostasis and immune processes and are induced by cell stress such as inflammation and infection. Autoimmune bullous disorders (AIBDs) and COVID-19 represent potentially life-threatening inflammatory and infectious diseases, respectively. A significant portion of AIBDs remain refractory to currently available immunosuppressive therapies, which may represent a risk factor for COVID-19, and suffer from treatment side-effects. Despite advances in vaccination, there is still a need to develop new therapeutic approaches targeting SARS-CoV-2, especially considering vaccine hesitancy, logistical distribution challenges, and breakthrough infections. In this mini review, we briefly summarize the role of targeting Hsp90/70 as a promising double-edged sword in the therapy of AIBDs and COVID-19.

IgM Deficiency in Autoimmune Blistering Mucocutaneous Diseases Following Various Treatments: Long Term Follow-Up and Relevant Observations.

IgM deficiency has been reported in patients with many autoimmune diseases treated with Rituximab (RTX). It has not been studied, in detail, in autoimmune mucocutaneous blistering diseases (AIMBD). Our objectives were: (i) Examine the dynamics of IgM levels in patients with and without RTX. (ii) Influence of reduced serum IgM levels on clinical and laboratory parameters. (iii) Explore the possible molecular and cellular basis for reduced serum IgM levels. This retrospective study that was conducted in a single-center from 2000 to 2020. Serial IgM levels were studied in 348 patients with five AIMBD (pemphigus vulgaris, pemphigus foliaceus, bullous pemphigoid, mucous membrane pemphigoid, and ocular cicatricial pemphigoid) and found decreased in 55 patients treated with RTX, IVIG, and conventional immunosuppressive therapy (CIST). Hence the incidence of decreased serum IgM is low. The incidence of decreased IgM in patients treated with RTX was 19.6%, in patients treated with IVIG and CIST, it was 52.8% amongst the 55 patients. IgM levels in the post-RTX group were statistically significantly different from the IVIG group (p<0.018) and CIST group (p<0.001). There were no statistically significant differences between the groups in other clinical and laboratory measures. Decreased serum IgM did not affect depletion or repopulation of CD19+ B cells. Patients in the three groups achieved clinical and serological remission, in spite of decreased IgM levels. Decrease in IgM was isolated, since IgG and IgA were normal throughout the study period. Decreased IgM persisted at the same level, while the patients were in clinical remission, for several years. In spite of persistent decreased IgM levels, the patients did not develop infections, tumors, other autoimmune diseases, or warrant hospitalization. Studies on IgM deficiency in knockout mice provided valuable insights. There is no universally accepted mechanism that defines decreased IgM levels in AIMBD. The data is complex, multifactorial, sometimes contradictory, and not well understood. Nonetheless, data in this study provides novel information that enhances our understanding of the biology of IgM in health and disease.

Circulating Metabolomic Signature in Generalized Pustular Psoriasis Blunts Monocyte Hyperinflammation by Triggering Amino Acid Response.

Generalized pustular psoriasis (GPP), the most grievous variant of psoriasis, is featured by dysregulated systemic inflammatory response. The cellular and molecular basis of GPP is poorly understood. Blood monocytes are key players of host defense and producers of inflammatory cytokines including IL-1ß. How the immune response of monocytes is affected by metabolic internal environment in GPP remains unclear. Here, we performed a metabolomic and functional investigation of GPP serum and monocytes. We demonstrated a significant increase in IL-1ß production from GPP monocytes. In GPP circulation, serum amyloid A (SAA), an acute-phase reactant, was dramatically increased, which induced the release of IL-1ß from monocytes in a NLRP3-dependent manner. Using metabolomic analysis, we showed that GPP serum exhibited an amino acid starvation signature, with glycine, histidine, asparagine, methionine, threonine, lysine, valine, isoleucine, tryptophan, tyrosine, alanine, proline, taurine and cystathionine being markedly downregulated. In functional assay, under amino acid starvation condition, SAA-stimulated mature IL-1ß secretion was suppressed. Mechanistically, at post-transcriptional level, amino acid starvation inhibited the SAA-mediated reactive oxygen species (ROS) formation and NLRP3 inflammasome activation. Moreover, the immune-modulatory effect of amino acid starvation was blocked by silencing general control nonderepressible 2 kinase (GCN2), suggesting the involvement of amino acid response (AAR) pathway. Collectively, our results suggested that decreased serum amino acids in GPP blunted the innate immune response in blood monocytes through AAR pathway, serving as a feedback mechanism preventing excessive inflammation in GPP.

Case Report and Review of the Literature: Bullous Skin Eruption After the Booster-Dose of Influenza Vaccine in a Pediatric Patient With Polymorphic Maculopapular Cutaneous Mastocytosis.

Vaccination is a well-known trigger for mast cell degranulation in subjects affected by mastocytosis. Nevertheless, there is no exact standardized protocol to prevent a possible reaction after a vaccine injection, especially for patients who have already presented a previous vaccine-related adverse event, considering that these patients frequently tolerate future vaccine doses. For this reason, we aim to share our experience at Meyer Children's University Hospital in Florence to raise awareness on the potential risk for future vaccinations and to discuss the valuable therapeutic strategies intended to prevent them, taking into account what is proposed by experts in literature. We describe the case of an 18-month-old female affected by a polymorphic variant of maculopapular cutaneous mastocytosis that presented an extensive bullous cutaneous reaction 24 hours after the second dose (booster dose) of inactivated-tetravalent influenza vaccine, treated with a single dose of oral corticosteroid therapy with betamethasone (0.1 mg/kg) and an oral antihistamine therapy with oxatomide (1 mg/kg/daily) for a week, until resolution. To the best of our knowledge, in the literature, no documented case of reaction to influenza vaccine in maculopapular cutaneous mastocytosis is described. Subsequently, the patient started a background therapy with ketotifen daily (0.05 mg/kg twice daily), a non-competitive H1-antihistamine, and a mast cell stabilizer (dual activity). A non-standardized pharmacological premedication protocol with an H1-receptor antagonist (oxatomide, 0.5 mg/kg) administered 12 hours before the immunizations, and a single dose of betamethasone (0.05 mg/kg) together with another dose of oxatomide (0.5 mg/kg) administered 2 hours before the injections was followed to make it possible for the patient to continue with the scheduled vaccinations. Indeed, no reactions were subsequently reported. Thus, in our experience, a background therapy with ketotifen associated with a premedication protocol made by two doses of oxatomide and a single dose of betamethasone was helpful to make possible the execution of the other vaccines. We suggest how in these children, it could be considered the idea of taking precaution when vaccination is planned, regardless of the kind of vaccine and if a dose of the same vaccine was previously received. However, international consensus needs to be reached to manage vaccinations in children with mastocytosis and previous adverse reactions to vaccines.

Biologics in autoimmune bullous diseases: Current scenario.

Autoimmune bullous diseases can be intraepidermal (pemphigus group of disorders) or subepidermal (pemphigoid group of disorders). The treatment of these disorders chiefly comprises corticosteroids and immunosuppressant adjuvants like azathioprine and mycophenolate mofetil. Autoantibodies are the main mediators of these diseases. Rituximab, a chimeric anti-CD20 monoclonal antibody targeting B-cells, has emerged as an excellent treatment option for refractory pemphigus vulgaris in the last decade. Since then, many new biologics have been proposed/explored for managing autoimmune bullous diseases. These hold potential for greater efficacy and lesser adverse effects than conventional immunosuppressants. In this review, we discuss the role of various biologics in the treatment of autoimmune bullous diseases, followed by a brief discussion on the drawbacks to their use and new developments in this area.

Subcorneal pustular dermatosis associated with IgG monoclonal gammopathy of undetermined significance.

Subcorneal pustular dermatosis is a rare chronic relapsing bullous neutrophilic dermatosis. Because it can be associated with monoclonal gammopathy of undetermined significance and multiple myeloma, screening for these conditions is necessary. Herein, we present a case of subcorneal pustular dermatosis, with concurrent monoclonal gammopathy of undetermined significance, successfully treated with acitretin.

Paraneoplastic pemphigus: Revised diagnostic criteria based on literature analysis.

BACKGROUND: Paraneoplastic pemphigus (PNP) is a rare autoimmune bullous disease classically associated with an underlying neoplasm. The heterogeneous clinical and histopathologic features of the disease make diagnosis challenging for clinicians. There are no formally accepted diagnostic criteria, and newer techniques for identifying antibodies directed against plakin proteins have largely replaced immunoprecipitation, the historic gold standard. METHODS: An analysis of 265 published cases of PNP was performed. The clinical, histopathologic, and immunologic features of PNP were assessed. RESULTS: Based on this review, we modified previous diagnostic criteria to capture 89.4% of PNP cases compared to 71.2% of cases captured by the most commonly referenced criteria devised by Camisa and Helm (p-value < 0.01, z-test; 95% CI [10.2, 33.6]). CONCLUSION: These revised diagnostic criteria address the variable clinical, histopathologic, and biochemical features of PNP, allowing physicians to have greater confidence in diagnosis of this rare and often fatal disease. The revised criteria include three major criteria and two minor criteria, whereby meeting either all three major criteria or two major and both minor criteria would fulfill a diagnosis of paraneoplastic pemphigus. The major criteria include (a) mucous membrane lesions with or without cutaneous involvement, (b) concomitant internal neoplasm, and (b) serologic evidence of anti-plakin antibodies. The minor criteria include (a) acantholysis and/or lichenoid interface dermatitis on histopathology and (b) direct immunofluorescence staining showing intercellular and/or basement membrane staining.

Subepithelial autoimmune bullous dermatoses disease activity assessment and therapy.

Subepidermal (subepithelial) autoimmune blistering dermatoses are a group of rare skin disorders characterized by the disruption of the dermal-epidermal junction through the action of autoantibodies. The fourth article in this continuing medical education series presents the current validated disease activity scoring systems, serologic parameters, treatments, and clinical trials for bullous pemphigoid, mucous membrane pemphigoid, epidermolysis bullosa acquisita, bullous systemic lupus erythematosus, anti-p200 pemphigoid, linear IgA bullous dermatosis, and dermatitis herpetiformis.

Subepithelial autoimmune blistering dermatoses: Clinical features and diagnosis.

Subepithelial autoimmune blistering dermatoses are a group of rare skin disorders that are characterized by the disruption of the dermal-epidermal junction through the action of autoantibodies. The third article in this continuing medical education series explores the background, epidemiology, clinical features, and diagnostic criteria of each of the major subepithelial autoimmune blistering dermatoses, including bullous pemphigoid, pemphigoid gestationis, lichen planus pemphigoides, mucous membrane pemphigoid, linear IgA bullous dermatosis, and dermatitis herpetiformis.

Intraepithelial autoimmune blistering dermatoses: Clinical features and diagnosis.

Intraepithelial autoimmune blistering dermatoses are a rare group of skin disorders characterized by the intraepithelial disruption of intercellular connections through the action of autoantibodies. The first article in this continuing medical education series explores the background, epidemiology, clinical features, and diagnostic criteria of each of the major intraepithelial autoimmune blistering dermatoses, including pemphigus foliaceus, pemphigus erythematosus, pemphigus herpetiformis, fogo selvagem, pemphigus vulgaris, pemphigus vegetans, drug-induced pemphigus, IgA pemphigus, IgG/IgA pemphigus, and paraneoplastic pemphigus/paraneoplastic autoimmune multiorgan syndrome.