Paraneoplastic pemphigus: A detailed case series from the Netherlands revealing atypical cases.

BACKGROUND: Paraneoplastic pemphigus (PNP) is an extremely rare life-threatening blistering autoimmune disease that is associated with an underlying neoplasm. There is a set diagnostic criterion for PNP, which is primarily based on a severe stomatitis and the detection of specific antibodies against envoplakin, periplakin and alpha-2-macroglobulin-like protein 1. However, it has become increasingly evident that there are patients with PNP that do not meet all the diagnostic criteria requirements. OBJECTIVES: The aim of this study was to analyse our cohort of Dutch patients and to define the atypical cases that did not meet the diagnostic criteria. METHODS: A retrospective case study of all known Dutch PNP patients of the past 25 years. Patients' clinical and immunological variables were thoroughly analysed and described. RESULTS: Twenty-four patients were included in this study. The results revealed several atypical patient cases that did not completely meet the set diagnostic criteria. Of the 24 patients, two patients presented without stomatitis, in three patients an underlying neoplasm could not be detected, and in two patients the presence of specific autoantibodies could not be demonstrated, although all other criteria for PNP were met. Finally, three of the 24 patients survived the disease. CONCLUSION: Although our findings showed similarities to previous studies and most of the patients met the criteria, there were a few atypical patient cases; highlighting the importance of not strictly adhering to the set criteria when making a diagnosis, as this can lead to a missed or late diagnosis. Thus, it is of crucial importance to combine clinical and elaborate laboratory results to confirm the diagnosis of PNP in suspected patients. Although PNP harbours an unfavourable prognosis in most cases, it might be resolved by timely treatment of the underlying cause.

S2k guidelines on the management of paraneoplastic pemphigus/paraneoplastic autoimmune multiorgan syndrome initiated by the European Academy of Dermatology and Venereology (EADV).

BACKGROUND: Paraneoplastic pemphigus (PNP), also called paraneoplastic autoimmune multiorgan syndrome (PAMS), is a rare autoimmune disease with mucocutaneous and multi-organ involvement. PNP/PAMS is typically associated with lymphoproliferative or haematological malignancies, and less frequently with solid malignancies. The mortality rate of PNP/PAMS is elevated owing to the increased risk of severe infections and disease-associated complications, such as bronchiolitis obliterans. OBJECTIVES: These guidelines summarize evidence-based and expert-based recommendations (S2k level) for the clinical characterization, diagnosis and management of PNP/PAMS. They have been initiated by the Task Force Autoimmune Blistering Diseases of the European Academy of Dermatology and Venereology with the contribution of physicians from all relevant disciplines. The degree of consent among all task force members was included. RESULTS: Chronic severe mucositis and polymorphic skin lesions are clue clinical characteristics of PNP/PAMS. A complete assessment of the patient with suspected PNP/PAMS, requiring histopathological study and immunopathological investigations, including direct and indirect immunofluorescence, ELISA and, where available, immunoblotting/immunoprecipitation, is recommended to achieve a diagnosis of PNP/PAMS. Detection of anti-envoplakin antibodies and/or circulating antibodies binding to the rat bladder epithelium at indirect immunofluorescence is the most specific tool for the diagnosis of PNP/PAMS in a patient with compatible clinical and anamnestic features. Treatment of PNP/PAMS is highly challenging. Systemic steroids up to 1.5 mg/kg/day are recommended as first-line option. Rituximab is also recommended in patients with PNP/PAMS secondary to lymphoproliferative conditions but might also be considered in cases of PNP/PAMS associated with solid tumours. A multidisciplinary approach involving pneumologists, ophthalmologists and onco-haematologists is recommended for optimal management of the patients. CONCLUSIONS: These are the first European guidelines for the diagnosis and management of PNP/PAMS. Diagnostic criteria and therapeutic recommendations will require further validation by prospective studies.

Use of Convolutional Neural Networks for the Detection of u-Serrated Patterns in Direct Immunofluorescence Images to Facilitate the Diagnosis of Epidermolysis Bullosa Acquisita.

The u-serrated immunodeposition pattern in direct immunofluorescence (DIF) microscopy is a recognizable feature and confirmative for the diagnosis of epidermolysis bullosa acquisita (EBA). Due to unfamiliarity with serrated patterns, serration pattern recognition is still of limited use in routine DIF microscopy. The objective of this study was to investigate the feasibility of using convolutional neural networks (CNNs) for the recognition of u-serrated patterns that can assist in the diagnosis of EBA. The nine most commonly used CNNs were trained and validated by using 220,800 manually delineated DIF image patches from 106 images of 46 different patients. The data set was split into 10 subsets: nine training subsets from 42 patients to train CNNs and the last subset from the remaining four patients for a validation data set of diagnostic accuracy. This process was repeated 10 times with a different subset used for validation. The best-performing CNN achieved a specificity of 89.3% and a corresponding sensitivity of 89.3% in the classification of u-serrated DIF image patches, an expert level of diagnostic accuracy. Experiments and results show the effectiveness of CNN approaches for u-serrated pattern recognition with a high accuracy. The proposed approach can assist clinicians and pathologists in recognition of u-serrated patterns in DIF images and facilitate the diagnosis of EBA.

Insights into clinical and diagnostic findings as well as treatment responses in patients with mucous membrane pemphigoid: A retrospective cohort study.

BACKGROUND: The variable clinical severity of mucous membrane pemphigoid (MMP) often leads to diagnostic and therapeutic delays. OBJECTIVE: To describe the characteristics of a large cohort of patients with MMP. METHODS: A retrospective review of clinical and diagnostic characteristics as well as treatment responses in 145 patients with MMP. RESULTS: Monosite involvement was seen in 41.4% and multisite involvement in 58.6% of the patients. The oral mucosa was affected in 86.9% of the patients, followed by the ocular mucosa (30.3%), skin (26.2%), genital mucosa (25.5%), nasal mucosa (23.4%), and pharyngeal and/or laryngeal mucosa (17.2%). Ocular disease developed during the disease course in 41.7% of patients with initially other mucosal site involvement. The malignancy rate was significantly higher in patients with autoantibodies against laminin-332 than in patients with MMP without laminin-332 autoantibodies (35.3% vs 10.9%, respectively; P = .007). Systemic immunosuppressive or immunomodulatory therapy was administered to 77.1% of the patients, mainly to patients with multisite (P < .001), ocular (P < .001), and pharyngeal and laryngeal involvement (P = .002). The remaining patients (22.9%) received topical therapy. Adverse events were frequently reported. LIMITATIONS: Retrospective design. CONCLUSION: Patients with MMP present with a heterogeneous clinical presentation, and new symptoms may develop during the disease course. Cancer screening should be considered for patients with MMP and, in particular, for those with autoantibodies against laminin-332.

Nonbullous pemphigoid: Insights in clinical and diagnostic findings, treatment responses, and prognosis.

BACKGROUND: Nonbullous pemphigoid is an under-recognized phenotype of the autoimmune bullous disease pemphigoid, characterized by the absence of blisters. Several disease aspects have not been studied previously. OBJECTIVE: To describe the characteristics of nonbullous pemphigoid. METHODS: A retrospective review study of medical records. The diagnosis of pemphigoid was based on meeting 2 of the following 3 criteria: (1) pruritus, (2) positive direct immunofluorescence microscopy, or (3) positive indirect immunofluorescence microscopy on salt-split skin. RESULTS: The review included 69 patients. The mean delay in diagnosis was 29 months. Skin examination most often showed pruritic papules/nodules (37%) or pruritus without primary skin lesions (22%). Histopathologic findings were mainly nonspecific. Results of direct and indirect immunofluorescence microscopy were positive in 60% and 69%, respectively. During follow-up, blisters formed in 17%, which was associated with a positive indirect immunofluorescence microscopy (P = .014) and a positive BP180 immunoblot result (P = .032). The Kaplan-Meier estimates of mortality at 1, 2, and 3 years were 14%, 34%, and 46%, respectively, with an 8.6-fold increased all-cause mortality risk. LIMITATIONS: The retrospective study design. CONCLUSIONS: Nonbullous pemphigoid presented with heterogeneous pruritic skin lesions, resulting in delayed diagnosis. Direct and indirect immunofluorescence microscopy are essential to diagnose nonbullous pemphigoid, in contrast to histopathology, mainly showing nonspecific findings. An increased all-cause mortality risk was observed during follow-up.

Nonbullous pemphigoid: A systematic review.

BACKGROUND: Bullous pemphigoid is an autoimmune disease that typically presents with tense bullae and severe pruritus. However, bullae can be lacking, a subtype termed nonbullous pemphigoid. OBJECTIVE: To summarize the reported characteristics of nonbullous pemphigoid. METHODS: The EMBASE and MEDLINE databases were searched using "nonbullous pemphigoid" and various synonyms. Case reports and series describing nonbullous pemphigoid were included. RESULTS: The search identified 133 articles. After selection, 39 articles were included, presenting 132 cases. Erythematous, urticarial plaques (52.3%) and papules/nodules (20.5%) were the most reported clinical features. The mean age at presentation was 74.9 years. Histopathology was commonly nonspecific. Linear depositions of IgG and/or C3 along the basement membrane zone were found by direct immunofluorescence microscopy in 93.2%. Indirect immunofluorescence on salt-split skin was positive in 90.2%. The mean diagnostic delay was 22.6 months. A minority of patients (9.8%) developed bullae during the reported follow-up. LIMITATIONS: Results are mainly based on case reports and small case series. CONCLUSION: Nonbullous pemphigoid is an underdiagnosed variant of pemphigoid that most often does not evolve to bullous lesions and mimics other pruritic skin diseases. Greater awareness among physicians is needed to avoid delay in diagnosis.

Serration pattern analysis for differentiating epidermolysis bullosa acquisita from other pemphigoid diseases.

BACKGROUND: Direct immunofluorescence (DIF) microscopy of a skin biopsy specimen is the reference standard for the diagnosis of pemphigoid diseases (PDs). Serration pattern analysis enables the differentiation of epidermolysis bullosa acquisita (EBA) from other PDs using DIF microscopy alone. However, practice gaps need to be addressed in order to implement this technique in the routine diagnostic procedure. OBJECTIVE: We sought to determine and optimize the technical requirements for serration pattern analysis of DIF microscopy and determine interrater conformity of serration pattern analysis. METHODS: We compared serration pattern analysis of routine DIF microscopy from laboratories in Groningen, The Netherlands and Lübeck, Germany with 4 blinded observers. Skin biopsy specimens from 20 patients with EBA and other PDs were exchanged and analyzed. Various factors were evaluated, including section thickness, transport medium, and biopsy specimen processing. RESULTS: The interrater conformity of our 4 observers was 95.7%. Recognition of serration patterns was comparable in samples transported in saline and in Michel's medium and with section thicknesses of 4, 6, and 8 µm. LIMITATIONS: Limitations include our small sample size and the availability of 20 samples that were compared retrospectively. CONCLUSION: DIF serration pattern analysis is not restricted by variation in laboratory procedures, transport medium, or experience of observers. This learnable technique can be implemented as a routine diagnostic method as an extension of DIF microscopy for subtyping PD.

Allergic contact dermatitis caused by dimethylthiocarbamylbenzothiazole sulfide (DMTBS) in canvas shoes: in search of the culprit allergen.

BACKGROUND: During rubber vulcanization, new compounds can be formed. OBJECTIVES: To report a case of allergic shoe dermatitis in which the search for the allergen ultimately led to the identification of dimethylthiocarbamylbenzothiazole sulfide (DMTBS). METHODS: A female presented with eczema on her feet after wearing Sperry Top Sider® canvas sneakers. Patch testing was performed with the European baseline series, additional series, shoe materials, and extracts of shoe materials. Thin-layer chromatography (TLC) was performed for additional patch testing, and high-performance liquid chromatography and gas chromatography-mass spectometry were used for chemical analysis. RESULTS: Positive reactions were found to thiuram mix (+), tetramethylthiuram monosulfide (TMTM) (+), shoe material (+), and shoe extracts in eth. (++) and acetone (+). The extracts did not contain TMTM or other components of thiuram mix. TLC strips yielded a positive reaction (+) to one spot, whereas chemical analysis gave a negative result. Thereafter, a similar sneaker from another patient with shoe dermatitis was analysed, and DMBTS was identified. New extracts of the shoe of our first patient were then also shown to contain DMTBS. DMTBS as culprit allergen was confirmed by positive patch testing with a dilution series with DMTBS. CONCLUSION: DMBTS was identified as the culprit allergen in shoe dermatitis, giving rise to compound allergy. The positive reaction to TMTM was considered to represent cross-reactivity.

Contact dermatitis caused by a new rubber compound detected in canvas shoes.

BACKGROUND: In 2015 and 2016, female patients in Flanders consulted a dermatologist because they developed skin lesions after wearing a specific brand of canvas shoes. OBJECTIVES: To identify the culprit allergen in the shoes. METHODS: Eighteen young females aged 14-22 years presented with itching and erythematous to purple-coloured eczematous lesions on both feet. They were patch tested by 10 dermatologists with the European baseline series. Some patients underwent testing with additional series. Pieces of the shoe fabrics were tested in 11 of 18 patients. Chemical analysis of the shoe materials was performed. Finally, patients were tested with a thin-layer chromatogram of the shoe extracts and dilutions of the suspected rubber compound. RESULTS: All 18 patients showed positive reactions to thiuram mix. Ten of 11 patients reacted to a piece of shoe fabric. Chemical analysis showed the presence of dimethylthiocarbamylbenzothiazole sulfide (DMTBS). No thiurams were detected. Four patients tested with the chromatogram developed positive reactions to DMTBS. Positive reactions to low concentrations were observed in the 4 patients tested with a DMTBS dilution series; one patient reacted to 0.00001% in acetone. CONCLUSIONS: DMTBS, the culprit allergen, is a component formed during rubber vulcanization that probably cross-reacts with the thiuram mix.

Simulation-based trauma education for medical students: A review of literature.

BACKGROUND: Medical students often do not feel prepared to manage emergency situations after graduation. They experience a lack of practical skills and show significant deficits in cognitive performance to assess and stabilize trauma patients. Most reports in the literature about simulation-based education pertain to postgraduate training. Simulation-based trauma education (SBTE) in undergraduate medical education could improve confidence and performance of recently graduated doctors in trauma resuscitation. We reviewed the literature in search of SBTE effectiveness for medical students. METHODS: A PubMed, Embase and CINAHL literature search was performed to identify all studies that reported on the effectiveness of SBTE for medical students, on student perception on SBTE or on the effectiveness of different simulation modalities. RESULTS: Eight studies were included. Three out of four studies reporting on the effectiveness of SBTE demonstrated an increase in performance of students after SBTE. SBTE is generally highly appreciated by medical students. Only one study directly compared two modalities of SBTE and reported favorable results for the mechanical model rather than the standardized live patient model. CONCLUSION: SBTE appears to be an effective method to prepare medical students for trauma resuscitation. Furthermore, students enjoy SBTE and they perceive SBTE as a very useful learning method.

Absence of Epidermal Antibodies in Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis Patients but Beware of Single Positive Results.

Background: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare and potentially life-threatening mucocutaneous blistering diseases that clinically can resemble autoimmune bullous diseases. Moreover, it has been shown that autoantibodies against epidermal proteins are present in SJS/TEN. Objectives: To establish the presence of antibodies against desmosomal and hemidesmosomal proteins in confirmed SJS/TEN patients. Methods: Serum of SJS/TEN patients diagnosed based on clinical criteria, e.g., epidermal detachment with erosions and severe mucosal lesions, (suspicion of) a culprit drug, and matching histologic results was evaluated by various techniques, e.g., indirect immunofluorescence on monkey esophagus, salt split skin and rat bladder, immunoblotting (IB) and immunoprecipitation (IP), ELISAs against desmogleins and BP180, keratinocyte footprint assay, and keratinocyte binding assay. Results: A total of 28 patients were included in this study, 15 men and 13 women with a mean age of 56 years. In most patients, none of the serological tests were positive. In two patients, an elevated DSG3 titer was found suspicious for pemphigus vulgaris. Three patients had elevated NC16a titers, suggesting bullous pemphigoid. However, in all these patients, no other tests were positive and in these patients, the biopsy for direct immunofluorescence showed no evidence for an autoimmune bullous disease. Three patients showed reactivity against rat bladder rat bladder; these were, however, completely negative for A2ML1, envoplakin, and periplakin in the IB as well as the IP. Conclusions: Serological analysis for desmosomal and hemidesmosomal antibodies is reliable to rule an autoimmune bullous disease in patients with suspected SJS/TEN. However, one should not rely on one single test method since false positive results can occur. Moreover, this study also makes it less plausible that antibodies against desmosomal and/or hemidesmosomal components are involved in the pathogenesis of SJS/TEN.

Assessment of Diagnostic Strategy for Mucous Membrane Pemphigoid.

IMPORTANCE: An accurate diagnosis of mucous membrane pemphigoid (MMP) is essential to reduce diagnostic and therapeutic delay. OBJECTIVE: To assess the diagnostic accuracy of direct immunofluorescence microscopy on mucosal biopsy specimens and immunoserology in a large cohort of patients with suspected MMP. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study was carried out in a single tertiary care center for blistering diseases between January 2002 and March 2019. Eligible participants were patients with suspected MMP and paired data on at least a mucosal biopsy specimen for direct immunofluorescence microscopy (DIF) and indirect immunofluorescence microscopy (IIF) on a human salt-split skin substrate (SSS). In addition, an optional DIF test on a skin biopsy specimen and one or more performed routine immunoserologic tests were analyzed. Data analysis was conducted from April 2019, to June 2020. MAIN OUTCOMES AND MEASURES: Diagnostic accuracy of DIF, IIF SSS, and immunoblot for BP180 and BP230. RESULTS: Of the 787 participants, 121 (15.4%) received the diagnosis of MMP (50 men [41.3%], 71 women [58.7%]; mean [SD] age at diagnosis, 60.1 [17.7] years). Sixty-seven of the patients with MMP (55.4%) had monosite involvement, of which oral site was the most frequently affected (51 [42.1%]). No significant difference was found between the sensitivity of DIF on a perilesional buccal biopsy and a normal buccal biopsy (89.3% vs 76.7%). Three patients with solitary ocular involvement showed a positive DIF of only the oral mucosa. In 6 patients with a negative mucosal DIF, a skin biopsy confirmed diagnosis of MMP. Overall, IIF SSS was less sensitive (44.6%), but highly specific (98.9%). The sensitivity of immunoblot (66.1%) was higher compared to SSS, but with lower specificity (91.3%). CONCLUSIONS AND RELEVANCE: This comparative diagnostic accuracy study of a cohort of 787 patients found a high sensitivity of a mucosal DIF biopsy for diagnosis of MMP, and lower sensitivity of serologic analysis. A biopsy can be taken from either perilesional or normal buccal mucosa. An additional DIF biopsy of another mucosal site or of affected or unaffected skin may increase the diagnostic yield and is recommended in patients with negative DIF results and high clinical suspicion.

Percutaneous transluminal angioplasty and stenting as first-choice treatment in patients with chronic mesenteric ischemia.

PURPOSE: Open revascularization in patients with chronic mesenteric ischemia (CMI) is considered the gold standard. Percutaneous transluminal angioplasty and stenting (PTAS) is often reserved for patients not suitable for open revascularization. In our institute, endovascular revascularization is the first-choice treatment. The purpose of this study was to report the technical and clinical success rates after endovascular revascularization as the first-choice treatment in a series of 51 consecutive patients with CMI at a single tertiary vascular referral center. METHODS: A retrospective review was performed of all consecutive patients with CMI who underwent PTAS from July 2001 to July 2008. Only symptomatic patients treated for atherosclerotic CMI were included. Patency was evaluated using computed tomography angiography (CTA). Kaplan-Meier curves were used to calculate patency rates of the treated mesenteric arteries. RESULTS: Sixty mesenteric arteries (30 celiac trunks, 24 superior mesenteric, and 6 inferior mesenteric arteries) were treated in 51 patients (26 men). Major morbidity was 4%. After dissection of the superior mesenteric artery (n = 1) and brachial artery (n = 1), respectively, both patients underwent endarterectomy and patch plasty. In three arteries, the lesion could not be crossed endovascularly and they were deemed immediate intention-to-treat failures. The initial technical success rate was 93%. No 30-day mortality was observed. Median follow-up was 25 months. During follow-up, 2 patients died from intestinal ischemia. Complete symptom relief was achieved in 78% of patients. Primary 1- and 2-year patency rates were 86% +/- 5% and 60% +/- 9%, respectively; primary-assisted patency rates were 88% +/- 5% and 79% +/- 7%, respectively. During follow-up, 6 patients underwent open revascularization due to failure of PTAS. CONCLUSION: The initial technical success rate of PTAS as first-choice treatment of CMI is >90%. The 2-year primary patency rate dropped to 60%, but symptomatic in-stent stenoses could often be treated successfully with renewed endovascular techniques. Including one conversion, 14% of patients needed open revascularization during follow-up.

An Unexpected Case of Late Fatal Central Venous Catheter Sepsis: A Case Report.

Introduction Central venous catheters (CVC) are associated with risks and complications. Complications like vessel perforation, thrombosis, infection with significant morbidity and mortality, knotting, and ventricular perforation have been described. Another less-frequent complication is retained CVC fragments. We present a case of a very late but fatal complication after a CVC placement. This report is written in line with the consensus-based surgical case report guidelines (SCARE). Case A 46-year-old male presented to the emergency department in a critical (septic) shock. The patients' medical history featured a long-intensive care admission 28 years ago. The cause of this sepsis was not evident until a computed tomography scan was performed to exclude a pulmonary embolism, revealing a remnant of a central catheter in both pulmonary arteries. Despite extensive resuscitation, the patient died within 24 hours after admission. An autopsy was performed confirming that the catheter remnant was the only possible cause of the fatal sepsis. Discussion CVC's are associated with (fatal) complications; however, retainment of remnants are described unfrequently but do occur in almost 2% of the cases. Endovascular removal of these remnants has been performed successfully and should be the first treatment of choice if removal is considered. No evidence is available that suggests that routine removal has to be attempted but some longer term complications can be expected, so awareness of possible remnants after CVC removal should exist. Conclusion Retained fragments of CVC's are rare but are described after prolonged use. This case shows that these retained intravascular fragments can cause fatal complications on the long-term. Upon removal of CVC's, there should be awareness that retainment of fragments can occur.

Oral Lesions in Autoimmune Bullous Diseases: An Overview of Clinical Characteristics and Diagnostic Algorithm.

Autoimmune bullous diseases are a group of chronic inflammatory disorders caused by autoantibodies targeted against structural proteins of the desmosomal and hemidesmosomal plaques in the skin and mucosa, leading to intra-epithelial or subepithelial blistering. The oral mucosa is frequently affected in these diseases, in particular, in mucous membrane pemphigoid, pemphigus vulgaris, and paraneoplastic pemphigus. The clinical symptoms are heterogeneous and may present with erythema, blisters, erosions, and ulcers localized anywhere on the oral mucosa, and lead to severe complaints for the patients including pain, dysphagia, and foetor. Therefore, a quick and proper diagnosis with adequate treatment is needed. Clinical presentations of autoimmune bullous diseases often overlap and diagnosis cannot be made based on clinical features alone. Immunodiagnostic tests are of great importance in differentiating between the different diseases. Direct immunofluorescence microscopy shows depositions of autoantibodies along the epithelial basement membrane zone in mucous membrane pemphigoid subtypes, or depositions on the epithelial cell surface in pemphigus variants. Additional immunoserological tests are useful to discriminate between the different subtypes of pemphigoid, and are essential to differentiate between pemphigus and paraneoplastic pemphigus. This review gives an overview of the clinical characteristics of oral lesions and the diagnostic procedures in autoimmune blistering diseases, and provides a diagnostic algorithm for daily practice.

Assessment of Diagnostic Strategy for Early Recognition of Bullous and Nonbullous Variants of Pemphigoid.

Importance: A substantial number of patients with bullous pemphigoid do not develop skin blisters and may not have received the correct diagnosis. Diagnostic criteria and an optimal diagnostic strategy are needed for early recognition and trials. Objectives: To assess the minimal requirements for diagnosis of bullous and nonbullous forms of pemphigoid and to evaluate the optimal diagnostic strategy. Design, Setting, and Participants: This paired, multivariable, diagnostic accuracy study analyzed data from 1125 consecutive patients with suspected pemphigoid who were referred to the Groningen Center for Blistering Diseases from secondary and tertiary care hospitals throughout the Netherlands. Eligible participants were patients with paired data on at least (1) a skin biopsy specimen for the direct immunofluorescence (DIF) microscopy test; (2) indirect immunofluorescence on a human salt-split skin substrate (IIF SSS) test; and (3) 1 or more routine immunoserologic tests administered between January 1, 2002, and May 1, 2015. Samples were taken from patients at the time of first diagnosis, before introduction of immunosuppressive therapy, and within an inclusion window of a maximum of 4 weeks. Data analysis was conducted from October 1, 2015, to December 1, 2017. Main Outcomes and Measures: Pairwise DIF, IIF SSS, IIF on monkey esophagus, BP180 and BP230 enzyme-linked immunosorbent assays, and immunoblot for BP180 and BP230 tests were performed. The results were reported in accordance with 2015 version of the Standards for Reporting Diagnostic Accuracy. Results: Of the 1125 patients analyzed, 653 (58.0%) were women and 472 (42.0%) were men, with a mean (SD) age of 63.2 (19.9) years. In total, 343 participants received a pemphigoid diagnosis, with 782 controls. Of the 343 patients, 74 (21.6%, or 1 in 5) presented with nonbullous pemphigoid. The DIF microscopy was the most sensitive diagnostic test (88.3% [n = 303]; 95% CI, 84.5%-91.3%), whereas IIF SSS was less sensitive (77.0% [n = 263]; 95% CI, 72.2%-81.1%) but was highly specific (99.9%; 95% CI, 99.3%-100%) and complemented most cases with negative DIF findings. Results of the BP180 NC16A enzyme-linked immunosorbent assay did not add diagnostic value for initial diagnosis in multivariable logistic regression analysis of combined tests. These findings lead to the proposed minimal criteria for diagnosing pemphigoid: (1) pruritus and/or predominant cutaneous blisters, (2) linear IgG and/or C3c deposits (in an n-serrated pattern) by DIF on a skin biopsy specimen, and (3) positive epidermal side staining of IgG by IIF SSS on a serum sample; this proposal extends bullous pemphigoid with the unrecognized nonbullous form. Conclusions and Relevance: Both DIF and IIF SSS tests should be performed for diagnosis of the bullous and nonbullous variants of pemphigoid, and the BP180 NC16A enzyme-linked immunosorbent assay is recommended as an add-on test for disease activity monitoring.