Co-occurrence of IgE and IgG autoantibodies in patients with chronic spontaneous urticaria.

Chronic spontaneous urticaria (CSU) pathogenesis shows a complex and still unclear interplay between immunoglobulin (Ig)G- and IgE-mediated autoimmunity, leading to mast cell and basophil degranulation and wheal formation. The objective of this study was to evaluate at the same time IgE- and IgG-reactivity to well recognized and recently reported autoantigens in CSU patients, and to assess the effects of such reactivity on response to the anti-IgE monoclonal antibody omalizumab. Twenty CSU patients underwent omalizumab treatment. Urticaria activity score 7 (UAS7) was recorded at baseline and at different drug administration time-points for categorizing early-, late- or non-responders. At baseline, sera from the 20 patients and from 20 controls were tested for IgE and IgG autoantibodies to high- and low-affinity IgE receptors (FcεRI and FcεRII), tissue factor (TF) and thyroglobulin (TG) by immunoenzymatic methods. Antibody levels were compared with those of controls and analysed according to response. Eighteen patients were omalizumab responders (11 early and seven late), while two were non-responders. More than 50% of patients had contemporary IgE and IgG to at least to one of the four different autoantigens. Late responders showed higher levels of both anti-TF IgE and IgG than early responders (P = 0·011 and P = 0·035, respectively). Twenty-five per cent of patients had levels of anti-FcεRI IgE, exceeding the upper normal limit, suggesting that it could be a novel auto-allergen in CSU. In CSU, there is an autoimmune milieu characterized by the co-existence of IgE and IgG autoantibodies to the same antigen/allergen, particularly in late responders to omalizumab, possibly explaining the slower response.

Involvement of the IgE-basophil system and mild complement activation in haemophilia B with anti-factor IX neutralizing antibodies and anaphylaxis.

INTRODUCTION: Patients with haemophilia B who develop factor IX (FIX) neutralizing antibodies (inhibitors) after FIX infusion are at high risk of hypersensitivity reactions upon FIX re-exposure, but the underlying mechanisms are incompletely understood. AIM: To investigate biomechanisms of FIX hypersensitivity. METHODS: A cellular antigen stimulation test (CAST) was employed to evaluate leukotriene C4 (LTC4) release from basophils stimulated by FIX in three treated children with haemophilia B, one of whom developed FIX inhibitor and experienced anaphylaxis following FIX re-exposure. Anti-FIX IgE and IgG antibodies and markers of complement activation (C5b9, C3d and iC3b) were measured in plasma, the last also after FIX infusion. Ten healthy children served as controls. RESULTS: The patient who developed anti-FIX inhibitors and anaphylaxis had a nonsense mutation in FIX gene (p.Arg298Stop) and, compared to controls, had higher plasma levels of specific anti-FIX IgE (2.285 vs 0.084 OD492 nm ), with marked LTC4 release from his FIX-stimulated basophils (519.8 vs 39.9 pg/mL). Further, he had higher plasma levels of anti-FIX IgG of all the four subclasses (total IgG 1.180 vs 0.120 OD492 nm ) with FIX neutralizing activity (1.5 BU); mild complement activation occurred during FIX-induced anaphylaxis (C5b9 increased from 258.5 to 351.1 ng/mL). The same parameters were normal in the two patients who tolerated FIX infusion. CONCLUSION: In the patient with haemophilia B who experienced anaphylaxis after FIX, but not in the patients with haemophilia B who tolerated FIX, the CAST assay showed FIX-induced LTC4 release, which was associated with high plasma levels of specific anti-FIX IgE and IgG antibodies.

Autoinflammation in pyoderma gangrenosum and its syndromic form (pyoderma gangrenosum, acne and suppurative hidradenitis).

BACKGROUND: Pyoderma gangrenosum (PG) is a rare skin disease characterized clinically by ulcers with undermined borders, and histologically by neutrophil-rich infiltrates. PG may occur alone, in syndromic forms or associated with systemic diseases, such as inflammatory bowel disease and haematological or rheumatological disorders. OBJECTIVES: To determine a specific genetic background related to autoinflammation for PG. METHODS: We assessed autoinflammation by evaluating the cytokine profile and genes involved in classic autoinflammatory diseases in 13 patients with PG and in seven patients with the syndromic form, known as PASH (pyoderma gangrenosum, acne and suppurative hidradenitis). RESULTS: In skin samples, the expression of interleukin (IL)-1ß and its receptors, IL-17 and its receptor, and tumour necrosis factor-α and its receptors were significantly higher in both PG (P = 0·001) and in PASH (P < 0·001) than in controls. The chemokines IL-8; chemokine (C-X-C motif) ligand 1/2/3; chemokine (C-X-C motif) ligand 16; and RANTES (regulated on activation, normal T-cell-expressed and secreted) were also overexpressed. Cases of PG and PASH showed mutations in the autoinflammatory genes MEFV, NLRP3, NLRP12, NOD2, LPIN2 and PSTPIP1. CONCLUSIONS: Overexpression of cytokines/chemokines, along with genetic changes, supports the hypothesis that PG and its syndromic form, PASH, are a spectrum of polygenic autoinflammatory conditions.

Detection of Low-Molecular-Weight Mast Cell-Activating Factors in Serum From Patients With Chronic Spontaneous Urticaria.

BACKGROUND AND OBJECTIVES: Functionally active autoantibodies to IgE and to the high-affinity IgE receptor (FcεRI) can be detected in serum in about 40% of patients with chronic spontaneous urticaria (CSU). Recent studies showed that serum from patients with CSU can induce activation of mast cells, irrespective of whether they carry high-affinity IgE receptors. To evaluate mast cell activation induced by factors in the serum of CSU patients with a molecular weight lower than that of autoantibodies. METHODS: Eight CSU patients and 5 healthy controls were evaluated. Whole serum and serum fractionated at 100, 50, and 30 kDa were used to stimulate in vitro LAD2 mast cells. The enzymatic activity of ß-hexosaminidase was evaluated in supernatants and cell pellets as a measure of mast cell degranulation. RESULTS: Mean (SEM) release of mast cell ß-hexosaminidase induced by whole serum from CSU patients was higher than that induced by serum from the healthy controls (14.4 [2.7%] vs 5.1 [2.4%]; P=.027). In addition, serum fractions below 100 kDa and below 50 kDa from CSU patients induced mast cell degranulation that was significantly higher than that induced by the corresponding fractions in sera from healthy controls (10.2% [1.4%] vs 3.8% [1.9%] [P=.024] and 10.1% [1.2%] vs 3.9% [1.7%] [P=.012], respectively). In 4 CSU patients, we evaluated serum fractions <30 kDa, which retained their capacity to activate mast cells (11.0% [0.7%]). CONCLUSIONS: This study shows that sera from CSU patients may contain low-molecular-weight mast cell-activating factors other than autoantibodies. These factors could be an additional mechanism contributing to the pathogenesis of CSU.

Pyoderma gangrenosum and its syndromic forms: evidence for a link with autoinflammation.

Pyoderma gangrenosum is a rare inflammatory neutrophilic dermatosis manifesting as painful ulcers with violaceous, undermined borders on the lower extremities. It may occur in the context of classic syndromes like PAPA (pyogenic arthritis, pyoderma gangrenosum and acne) and SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis), as well as in a recently described entity named PASH (pyoderma gangrenosum, acne and suppurative hidradenitis). Pyoderma gangrenosum has recently been included within the spectrum of autoinflammatory diseases, which are characterized by recurrent episodes of sterile inflammation, without circulating autoantibodies and autoreactive T cells. In PAPA syndrome, different mutations involving the PSTPIP1 gene, via an increased binding affinity to pyrin, induce the assembly of inflammasomes. These are molecular platforms involved in the activation of caspase 1, a protease that cleaves inactive prointerleukin (pro-IL)-1ß to its active isoform IL-1ß. The overproduction of IL-1ß triggers the release of a number of proinflammatory cytokines and chemokines, which are responsible for the recruitment and activation of neutrophils, leading to neutrophil-mediated inflammation. In SAPHO syndrome, the activation of the PSTPIP2 inflammasome has been suggested to play a role in inducing the dysfunction of the innate immune system. Patients with PASH have recently been reported to present alterations of genes involved in well-known autoinflammatory diseases, such as PSTPIP1, MEFV, NOD2 and NLRP3. Pyoderma gangrenosum and its syndromic forms can be regarded as a single clinicopathological spectrum in the context of autoinflammation.

Thrombotic microangiopathy without renal involvement: two novel mutations in complement-regulator genes.

UNLABELLED: ESSENTIALS: The differential diagnosis among thrombotic microangiopathies (TMAs) is challenging. We studied a case of TMA with neurologic symptoms, no renal impairment and normal ADAMTS-13 levels. Two novel mutations in complement factor I and thrombomodulin genes were identified. Complement-regulator genes can be involved in TMAs with normal ADAMTS-13 regardless of renal damage. BACKGROUND: Thrombotic microangiopathies (TMAs) often represent a challenge for clinicians, because clinical, laboratory, and even genetic features are not always sufficient to distinguish among different TMAs. OBJECTIVES: The aim of this study was to investigate the pathogenetic mechanisms underlying an acute case of TMA with features of both thrombotic thrombocytopenic purpura (TTP) and atypical hemolytic uremic syndrome (aHUS). PATIENTS/METHODS: We report the case of a 49-year-old woman who developed an acute TMA with neurologic involvement and no renal impairment. ADAMTS-13, von Willebrand factor, and complement-system biochemical characterization was performed on acute phase samples. Exome sequencing and direct Sanger sequencing of previously aHUS-associated genes were performed. The functional consequences of the thrombomodulin (THBD) mutation were investigated by in vitro expression studies. RESULTS: Despite a clinical diagnosis of TTP, the patient had normal ADAMTS-13 levels and increased VWF antigen levels with ultra-large von Willebrand factor multimers. C3, C4, and complement factors H and I (CFI) were normal. Molecular analysis confirmed two novel heterozygous mutations in CFI (c.805G>A, p.G269S) and THBD (c.1103C>T, p.P368L), and in vitro expression studies showed a reduction in the generation of activated thrombin-activatable fibrinolysis inhibitor (TAFIa) caused by mutated THBD. This proinflammatory condition, associated with the p.G269S mutation in CFI, probably leads to a complement-mediated endothelial activation, with a relevant prothrombotic potential in case of transient environmental triggers. CONCLUSIONS: This study identified the first case of acute TMA without renal involvement but with neurological damage carrying two novel mutations in complement-regulator genes, highlighting the possible role of the complement system as a common pathogenetic mechanism in TMAs.

Detection of low-molecular-weight mast cell-activating factors in serum from patients with chronic spontaneous urticaria

Background: Functionally active autoantibodies to IgE and to the high-affinity IgE receptor (FcεRI) can be detected in serum in about 40% of patients with chronic spontaneous urticaria (CSU). Recent studies showed that serum from patients with CSU can induce activation of mast cells, irrespective of whether they carry high-affinity IgE receptors. Objective: To evaluate mast cell activation induced by factors in the serum of CSU patients with a molecular weight lower than that of autoantibodies. Methods: Eight CSU patients and 5 healthy controls were evaluated. Whole serum and serum fractionated at 100, 50, and 30 kDa were used to stimulate in vitro LAD2 mast cells. The enzymatic activity of β-hexosaminidase was evaluated in supernatants and cell pellets as a measure of mast cell degranulation. Results: Mean (SEM) release of mast cell β-hexosaminidase induced by whole serum from CSU patients was higher than that induced by serum from the healthy controls (14.4 [2.7%] vs 5.1 [2.4%]; P =.027). In addition, serum fractions below 100 kDa and below 50 kDa from CSU patients induced mast cell degranulation that was significantly higher than that induced by the corresponding fractions in sera from healthy controls (10.2% [1.4%] vs 3.8% [1.9%] [P=.024] and 10.1% [1.2%] vs 3.9% [1.7%] [P=.012], respectively). In 4 CSU patients, we evaluated serum fractions <30 kDa, which retained their capacity to activate mast cells (11.0% [0.7%]). Conclusions: This study shows that sera from CSU patients may contain low-molecular-weight mast cell-activating factors other than autoantibodies. These factors could be an additional mechanism contributing to the pathogenesis of CSU (AU)

Introducción: Los autoanticuerpos IgE funcionalmente activos y los receptores de alta afinidad para la IgE (FcεRI) pueden ser detectados n el suero de aproximadamente un 40% de los pacientes con urticaria crónica espontánea (UCE). Estudios recientes muestran que el uero de estos pacientes puede inducir activación de mastocitos con o sin receptores de alta afinidad para la IgE. Objetivo: El objetivo de este estudio fue evaluar la actividad de los factores séricos de los sueros de pacientes con UCE con un peso molecular inferior al de los autoanticuerpos. Métodos: Para ello se estudiaron 8 pacientes con UCE y 5 controles sanos. El suero completo de cada uno de ellos y el fraccionado a 100,50 y 30 kDA se utilizó para estimular in vitro mastocitos LAD2. La actividad enzimática de la β-hexosaminidasa se determinó en los sobrenadantes y en el botón celular con el fin de cuantificar la degranulación mastocitaria. Resultados: En cuanto a los resultados obtenidos se observó una liberación de β-hexosaminidasa mastocitaria inducida por los sueros completos de los pacientes con UCE (14,4±2,7%, media ± EE de la media) significativamente mayor que la inducida por sueros de controles sanos (5,1±2,4%; p=0,027). Así mismo, las fracciones séricas inferiores a 100 kDa e inferiores a 50 kDa de los pacientes con UCE indujeron degranulación mastocitaria significativamente superior a la inducida por las fracciones correspondientes de sueros controles (10,2±1,4% vs 3,8±1,9% [p=0,024] and 10,1±1,2% vs 3,9±1,7% [p=0,012], respectivamente). En 4 pacientes con UCE observamos que las fracciones inferiores a 30 kDa mantenían la capacidad de activar a los mastocitos (11,0±0,7%). Conclusiones: En conclusión, este estudio muestra que el suero de los pacientes con UCE puede contener factores de bajo peso molecular diferentes a los autoanticuerpos que son capaces de activar a los mastocitos. Este hallazgo podría contribuir a conocer los mecanismos de la patogénesis de la UCE (AU)

The complex differential diagnosis between thrombotic thrombocytopenic purpura and the atypical hemolytic uremic syndrome: Laboratory weapons and their impact on treatment choice and monitoring.

Thrombocytopenia and microangiopathic hemolytic anemia are the hallmark of the thrombotic microangiopathies (TMAs) thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). TTP, inherited or autoimmune, is mainly caused by the plasma deficiency of the von Willebrand factor cleaving protease ADAMTS13, owing to gene mutations or autoantibodies. Typical HUS is often caused by infections with Shiga-Toxin-producing Escherichia coli and thus is called STEC-HUS. The rarer atypical form of HUS is often associated with complement dysregulation, owing to the inherited deficiency or dysfunction of factor H or other complement proteins. In the past the distinction between these TMAs was almost exclusively based on clinical grounds, the term TTP being used for cases with predominant neurological involvement, STEC HUS for cases presenting with bloody diarrhea and atypical HUS identifying patients with severe renal damage. However the clinical presentation may not easily distinguish TTP from atypical HUS. A more accurate differential diagnosis has clinical implications, because plasma exchange (the treatment of choice in TTP) is much less effective in atypical HUS, which shows dramatic short- and long-term therapeutic benefits from eculizumab, a monoclonal antibody that inhibits complement activation. This article will point out that the measurement of ADAMTS13 is able to diagnose accurately the majority of TTP cases, and that very simple tests such as the platelet count and serum creatinine can predict the deficiency of the protease with a good degree of accuracy. In atypical HUS, new methods were recently developed that not only demonstrate the activation of the complement system, i.e., the main disease mechanism, but also help to tailor the short- and long-term treatment with eculizumab.

Eosinophil cationic protein levels parallel coagulation activation in the blister fluid of patients with bullous pemphigoid.

BACKGROUND: Bullous pemphigoid (BP) is an autoimmune blistering disease due to autoantibodies against two hemidesmosomal antigens, namely BP180 and BP230, and characterized by coagulation activation both at cutaneous and systemic levels. Skin-infiltrating eosinophils contribute to bulla formation and, upon activation, are supposed to initiate the coagulation cascade. OBJECTIVE: The aim of this study was to investigate whether the activation of eosinophils and coagulation are linked in BP. METHODS: We evaluated the correlation between eosinophil cationic protein (ECP) levels and concentrations of the prothrombotic markers F1 + 2 and D-dimer in blister fluid and blood samples of 30 BP patients. Thirty healthy subjects were used as normal controls. RESULTS: ECP, F1 + 2 and D-dimer plasma levels were significantly higher in BP patients than in normal subjects. A significant correlation was found between ECP plasma levels and blood eosinophil count (r = 0.54, P = 0.002). F1 + 2 plasma levels positively correlated with disease severity, expressed as the percentage of body surface area involved (r = 0.36, P = 0.048). A striking increase in ECP (288.8 ± 45.2 ng/mL), F1 + 2 (31 409.9 ± 2929.4 pmol/L) and D-dimer levels (342 798.3 ± 44 206 ng/mL) was found in blister fluid from BP patients. In blister fluid, ECP levels were significantly higher than in peripheral blood (P < 0.0001) and were positively correlated with the levels of both F1 + 2 (r = 0.4, P = 0.02) and D-dimer (r = 0.5, P = 0.0045). CONCLUSIONS: ECP levels are strikingly elevated in blister fluids from BP patients and correlate with markers of coagulation activation, supporting the view that eosinophils initiate the coagulation cascade at skin level.

Expression of cytokines, chemokines and other effector molecules in two prototypic autoinflammatory skin diseases, pyoderma gangrenosum and Sweet's syndrome.

Pyoderma gangrenosum (PG) and Sweet's syndrome (SS) are two inflammatory skin diseases presenting with painful ulcers and erythematous plaques, respectively; both disorders have a debilitating clinical behaviour and PG is potentially life-threatening. Recently, PG and SS have been included among the autoinflammatory diseases, which are characterized by recurrent episodes of sterile inflammation, without circulating autoantibodies and autoreactive T cells. However, an autoinflammatory pattern clearly supporting this inclusion has never been demonstrated. We studied 16 patients with PG, six with SS and six controls, evaluating, using a sandwich-based protein antibody array method, the expression profile of inflammatory effector molecules in PG, SS and normal skin. The expressions of interleukin (IL)-1 beta and its receptor I were significantly higher in PG (P = 0·0001 for both) and SS (P = 0·004-0·040) than in controls. In PG, chemokines such as IL-8 (P = 0·0001), chemokine (C-X-C motif) ligand (CXCL) 1/2/3 (P = 0·002), CXCL 16 (P = 0·003) and regulated upon activation normal T cell expressed and secreted (RANTES) (P = 0·005) were over-expressed. In SS, IL-8 (P = 0·018), CXCL 1/2/3 (P = 0·006) and CXCL 16 (P = 0·036) but not RANTES were over-expressed, suggesting that chemokine-mediated signals are lower than in PG. Fas/Fas ligand and CD40/CD40 ligand systems were over-expressed in PG (P = 0·0001 for Fas, P = 0·009 for Fas ligand, P = 0·012 for CD40, P = 0·0001 for CD40 ligand), contributing to tissue damage and inflammation, while their role seems to be less significant in SS. Over-expression of cytokines/chemokines and molecules amplifying the inflammatory network supports the view that PG and SS are autoinflammatory diseases. The differences in expression profile of inflammatory effectors between these two disorders may explain the stronger local aggressiveness in PG than SS.

Complement functional tests for monitoring eculizumab treatment in patients with atypical hemolytic uremic syndrome.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy characterized by hemolysis, platelet consumption, and renal injury. Eculizumab, a mAb that blocks complement activity, has been successfully used in aHUS. OBJECTIVES: To optimize eculizumab therapy in aHUS patients by monitoring complement functional tests and markers of disease activity. PATIENTS/METHODS: We studied 18 patients with aHUS (10 males; eight females; age range, 2-40 years) treated with eculizumab to induce and/or maintain disease remission. Patients were followed up for a cumulative observation period of 160 months, during which blood samples were obtained at various time intervals to measure complement activity (Wieslab for the classical, alternative and mannose-binding lectin complement pathways) and the parameters of disease activity (haptoglobin and lactate dehydrogenase serum levels, and platelet count). The intravenous eculizumab doses of 12-33 mg kg(-1) were initially administered every week, with the interval between doses being gradually extended to 2 weeks, 3 weeks and 4 weeks on the basis of strict laboratory and clinical control. RESULTS: Complement activity was normal before eculizumab treatment, regardless of the state of the disease (activity or remission). It was completely suppressed 1 week, 2 weeks and 3 weeks after the last eculizumab infusion (mean values ± standard deviation: 1% ± 1% to 3% ± 5% for both the classical and alternative pathways; P = 0.0001 vs. baseline), and partially suppressed after 4 weeks (22% ± 26% and 16% ± 27%; P = 0.0001 vs. baseline). The increase in the time interval between eculizumab infusions did not change disease activity markers. CONCLUSIONS: Monitoring complement tests can allow a safe reduction in the frequency of eculizumab administration in aHUS while keeping the disease in remission.

Chronic urticaria and coagulation: pathophysiological and clinical aspects.

Chronic urticaria (CU) is a widespread skin disease, characterized by the recurrence of transient wheals and itch for more than 6 weeks. Besides autoimmune mechanisms, coagulation factors, in particular tissue factor and thrombin, might also participate in the disease pathophysiology. Tissue factor expressed by eosinophils can induce activation of blood coagulation generating thrombin which in turn can increase vascular permeability both directly, acting on endothelial cells, and indirectly, inducing degranulation of mast cells with release of histamine, as demonstrated in experimental models. D-dimer, a fibrin degradation product, generated following activation of the coagulation cascade and fibrinolysis, has been found to be increased during urticaria exacerbations; moreover, it has been proposed as a biomarker of severity and resistance to H1-antihistamines in CU patients. The possible role of coagulation in CU is also supported by case reports, case series and a small controlled study showing the efficacy of anticoagulant therapy in this disease. The purpose of this review was to summarize the available data on the possible contribution of coagulation to the pathophysiology of CU focusing on clinical aspects and possible future therapeutic developments.

High-molecular-weight kininogen cleavage correlates with disease states in the bradykinin-mediated angioedema due to hereditary C1-inhibitor deficiency.

BACKGROUND: The inherited deficiency of C1-inhibitor (C1-INH), which can be quantitative (type I) or qualitative (type II), is characterized by recurrent attacks of oedema, and it is known as hereditary angioedema due to C1-INH deficiency (HAE-C1-INH). The frequency of symptoms varies widely among patients and in the same patient during life. OBJECTIVE: To identify laboratory markers of disease severity in HAE-C1-INH patients. METHODS: We studied 162 patients with differently severe HAE-C1-INH during remission, 31 HAE-C1-INH patients during attacks, and 81 normal controls, evaluating complement parameters, spontaneous plasma kallikrein activity, the capacity of plasma to inhibit exogenous kallikrein activity, and cleavage of high-molecular-weight kininogen (HK). Sixty-five HAE-C1-INH patients were screened for mutations in the C1-INH gene. RESULTS: As expected, plasma C1-INH levels and activity and C4 levels were low in the HAE-C1-INH patients. Spontaneous plasma kallikrein activity in patients in remission was higher than in controls (P = 0.001) and increased during acute attacks (P = 0.01), whereas the capacity of inhibiting kallikrein activity was lower in patients in remission than in controls (P = 0.001) and further reduced during attacks (P = 0.001). HAE-C1-INH patients in remission had higher levels of cleaved HK than controls (P = 0.001), and these further increased during acute attacks (P = 0.001). Cleaved HK levels were higher in highly symptomatic HAE-C1-INH patients than in those with less frequent attacks (P = 0.001). Thirty-five different mutations in the C1-INH gene were equally distributed in patients with different attack frequencies. CONCLUSIONS: Measuring plasma levels of cleaved HK may be a sensitive mean of assessing disease severity in HAE-C1-INH patients.

Recurrent Angioedema Associated With Secondary Eosinophilia

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Diagnosis and disease severity assessment of epidermolysis bullosa acquisita by ELISA for anti-type VII collagen autoantibodies: an Italian multicentre study.

BACKGROUND: Epidermolysis bullosa acquisita (EBA) is a rare autoimmune mucocutaneous bullous disease caused by autoantibodies against type VII collagen, a component of anchoring fibrils that stabilizes dermoepidermal adherence. Type VII collagen is composed of a collagenous domain linked by the noncollagenous (NC)1 and NC2 domains. OBJECTIVES: To assess the repeatability, sensitivity and specificity of a recently developed enzyme-linked immunosorbent assay (ELISA) for detection of anti-type VII collagen autoantibodies, and to ascertain whether they may be a marker of disease activity in EBA. METHODS: Using this ELISA, which was able to recognize autoantibodies against the NC1 and NC2 epitopes of type VII collagen, we tested 14 EBA sera, 30 healthy control sera and 113 disease control sera. RESULTS: In the EBA sera group, 12 out of the 14 samples were positive in ELISA, with autoantibody titres varying from 7·2 to 127·9UmL(-1) (cutoff value <6), the sensitivity of the method being 86%. Among the controls, only two bullous pemphigoid sera tested positive, the specificity being 98·6%. A good correlation was found between EBA disease severity, expressed as autoimmune bullous skin disorder intensity score, and the serum levels of anti-collagen VII autoantibodies, measured by ELISA (n =14; r=0·965; P=0·0001). The intra- and interassay coefficients of variation of the ELISA method ranged from 6·3% to 18·3%. CONCLUSIONS: This NC1+NC2 ELISA can be a practical assay for the diagnosis of EBA. The correlation between autoantibody titres and disease severity suggests its usefulness as a marker of disease activity in EBA However, this should be confirmed by studies on larger series of patients.