HLA type as a predictor of mixed connective tissue disease differentiation. Ten-year clinical and immunogenetic followup of 46 patients

Clinical presentation, course, and prognosis of patients with mixed connective tissue disease: A multicenter retrospective cohort

OBJECTIVES

The objective of this study is to better characterize the features and outcomes of a large population of patients with mixed connective tissue disease (MCTD).

METHODS

We performed an observational retrospective multicenter cohort study in France. Patients who fulfilled at least one diagnostic criterion set for MCTD and none of the criteria for other differentiated CTD (dCTD) were included.

RESULTS

Three hundred and thirty patients (88% females, median [interquartile range] age of 35 years [26-45]) were included. The diagnostic criteria of Sharp or Kasukawa were met by 97.3% and 93.3% of patients, respectively. None met other classification criteria without fulfilling Sharp or Kasukawa criteria. After a median follow-up of 8 (3-14) years, 149 (45.2%) patients achieved remission, 92 (27.9%) had interstitial lung disease, 25 (7.6%) had pulmonary hypertension, and 18 (5.6%) died. Eighty-five (25.8%) patients progressed to a dCTD, mainly systemic sclerosis (15.8%) or systemic lupus erythematosus (10.6%). Median duration between diagnosis and progression to a dCTD was 5 (2-11) years. The presence at MCTD diagnosis of an abnormal pattern on nailfold capillaroscopy (odds ratio [OR] = 2.44, 95% confidence interval [95%CI] [1.11-5.58]) and parotid swelling (OR = 3.86, 95%CI [1.31-11.4]) were statistically associated with progression to a dCTD. Patients who did not progress to a dCTD were more likely to achieve remission at the last follow-up (51.8% vs. 25.9%).

CONCLUSIONS

This study shows that MCTD is a distinct entity that can be classified using either Kasukawa or Sharp criteria, and that only 25.8% of patients progress to a dCTD during follow-up.

Longitudinal follow-up of mixed connective tissue disease and overlapping autoimmune diseases of childhood onset in the Afro-descendant population of the French West Indies

INTRODUCTION

Overlap autoimmune syndromes (OAS) and mixed connective tissue disease (MCTD) are rare in children. We performed a retrospective, longitudinal and descriptive study of Afro-Caribbean patients from the French West Indies followed for MCTD and OAS to describe their characteristics and outcomes during childhood.

METHODS

Retrospective study from January 2000 to 2023. Listings of patients were obtained from multiple sources: computerized hospital archives and national hospital-based surveillance system, registry of pediatricians and adult specialists in internal medicine and the national registry for rare diseases. MCTD was defined according to Kasukawa's criteria. OAS was defined as overlapping features of systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and dermatomyositis/autoimmune myositis (DM/AM).

RESULTS

Sixteen patients were included over a 23-year period (10 MCTD and 6 OAS). The incidence was 0.23 per 100,000 children-years. The mean age at diagnosis was 11.9 years old (2.4-17) with median follow up of 7.9 years (2.1-19.6). SLE phenotype was present in the highest, followed by SSc and DM/AM. Patients had an average of three flares during childhood (1-7). A quarter (25%) had symptomatic pulmonary arterial hypertension (PAH). Ninety-four percent received steroids during follow-up and 88% required a corticosteroid-sparing therapy. Three patients (19%) developed SLE after more than 10y of follow-up. There were no death and no chronic organ failure.

CONCLUSION

This is the largest pediatric cohort of MCTD and OAS in Afro-descendant patients treated in a country with a high standard of care. The clinical evolution did not differ between MCTD and OAS. The main complication was PAH, more frequent in our cohort.

The diagnostic challenge of patients with anti-U1-RNP antibodies

Anti-U1-RNP antibodies are necessary for the diagnosis of mixed connective tissue disease (MCTD), but they are also prevalent in other connective tissue diseases, especially systemic lupus erythematosus (SLE), from which distinction remains challenging. We aimed to describe the presentation and outcome of patients with anti-U1-RNP antibodies and to identify factors to distinguish MCTD from SLE. We retrospectively applied the criteria sets for MCTD, SLE, systemic sclerosis (SSc) and rheumatoid arthritis (RA) to all patients displaying anti-U1-RNP antibodies in the hospital of Caen from 2000 to 2020. Thirty-six patients were included in the analysis. Eighteen patients (50%) satisfied at least one of the MCTD classifications, 11 of whom (61%) also met 2019 ACR/EULAR criteria for SLE. Twelve other patients only met SLE without MCTD criteria, and a total of 23 patients (64%) met SLE criteria. The most frequent manifestations included Raynaud's phenomenon (RP, 91%) and arthralgia (67%). We compared the characteristics of patients meeting only the MCTD (n = 7), SLE (n = 12), or both (n = 11) criteria. Patients meeting the MCTD criteria were more likely to display SSc features, including sclerodactyly (p < 0.01), swollen hands (p < 0.01), RP (p = 0.04) and esophageal reflux (p < 0.01). The presence of scleroderma features (swollen hands, sclerodactyly, gastro-oesophageal reflux), was significantly associated with the diagnosis of MCTD. Conversely, the absence of those manifestations suggested the diagnosis of another definite connective tissue disease, especially SLE.

The enigma of mixed connective tissue disease-challenges in routine care

Objectives

As a rare and heterogeneous disease, mixed connective tissue disease (MCTD) represents a challenge. Herein, we aimed to unravel potential pitfalls including correct referral diagnosis, distinction from other connective tissue diseases (CTD) and treatment modalities.

Methods

We characterised the MCTD cohort at our tertiary referral centre. All patients were evaluated for fulfilment of classification criteria of various CTDs. SLEDAI-2 K and EUSTAR-AI were used in accordance with previous research to evaluate disease activity and treatment response.

Results

Out of 85 patients initially referred as MCTD, only one-third (33/85, 39%) fulfilled the diagnostic MCTD criteria and the other patients had undifferentiated CTD (16/85, 19%), non-MCTD overlap syndromes (11/85, 13%) and other rheumatic diseases. In our final cohort of 33 MCTD patients, 16 (48%) also met the diagnostic criteria of systemic sclerosis, 13 (39%) these of systemic lupus erythematosus, 6 (18%) these of rheumatoid arthritis and 3 (9%) these of primary myositis. Management of MCTD required immunomodulating combination therapy in most cases (15/28, 54%), whereas monotherapy was less frequent (10/28, 36%), and only a few (3/28, 11%) remained without immune modulators until the end of the follow-up period. Treatment led to a significant decline in disease activity.

Conclusions

Our study showed a high risk for misdiagnosis for patients with MCTD. As a multi-organ disease, MCTD required prolonged immunomodulating therapy to achieve remission. The establishment of an international registry with longitudinal data from observational multi-centre cohorts might represent a first step to address the many unmet needs of MCTD.

Predisposition of HLA-DRB1*04:01/*15 heterozygous genotypes to Japanese mixed connective tissue disease

Mixed connective tissue disease (MCTD) is a rare systemic autoimmune disease characterized by the production of anti-U1 ribonucleoprotein antibodies and systemic symptoms similar to those of some other autoimmune diseases. HLA-DRB1 polymorphisms are important genetic risk factors for MCTD, but precise associations of DRB1 genotypes with MCTD have not been reported in Japanese people. Genotyping of HLA-DRB1 and -DQB1 was performed in Japanese MCTD patients (n = 116) and controls (n = 413). Associations of specific allele carriers and genotype frequencies with MCTD were analyzed.The following alleles were found to be associated with predisposition to MCTD: HLA-DRB1*04:01 (P = 8.66 × 10^–6, Pc = 0.0003, odds ratio [OR] 7.96, 95% confidence interval [CI] 3.13‒20.24) and DRB1*09:01 (P = 0.0189, Pc = 0.5468, OR 1.73, 95% CI 1.12‒2.67). In contrast, the carrier frequency of the DRB1*13:02 allele (P = 0.0032, Pc = 0.0929, OR 0.28, 95% CI 0.11‒0.72) was lower in MCTD patients than in controls. The frequencies of heterozygosity for HLA-DRB1*04:01/*15 (P = 1.88 × 10^–7, OR 81.54, 95% CI 4.74‒1402.63) and DRB1*09:01/*15 (P = 0.0061, OR 2.94, 95% CI 1.38‒6.25) were also higher in MCTD patients. Haplotype and logistic regression analyses suggested a predisposing role for HLA-DRB1*04:01, DQB1*03:03, and a protective role for DRB1*13:02. Increased frequencies of HLA-DRB1*04:01/*15 and DRB1*09:01/*15 heterozygous genotypes were found in Japanese MCTD patients.

"Mixed connective tissue disease": a condition in search of an identity

Mixed connective tissue disease was first described as a new autoimmune rheumatic disease in 1972 based on the claim of a distinct clinical picture associated with anti-RNP antibody positivity. Subsequently, this new entity has divided opinions in the rheumatology community. We have reviewed recent cohort studies with more than 100 patients, comparing the clinical and immunological features, treatment, prognosis and evolution to well-defined autoimmune rheumatic diseases. We also reviewed clinical features of undifferentiated autoimmune rheumatic diseases based on the most recent studies. After gathering and reviewing these data, we discuss whether the designation “mixed connective tissue disease” should be maintained.

Epigenome-Wide Comparative Study Reveals Key Differences Between Mixed Connective Tissue Disease and Related Systemic Autoimmune Diseases

Mixed Connective Tissue Disease (MCTD) is a rare complex systemic autoimmune disease (SAD) characterized by the presence of increased levels of anti-U1 ribonucleoprotein autoantibodies and signs and symptoms that resemble other SADs such as systemic sclerosis (SSc), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE). Due to its low prevalence, this disease has been very poorly studied at the molecular level. We performed for the first time an epigenome-wide association study interrogating DNA methylation data obtained with the Infinium MethylationEPIC array from whole blood samples in 31 patients diagnosed with MCTD and 255 healthy subjects. We observed a pervasive hypomethylation involving 170 genes enriched for immune-related function such as those involved in type I interferon signaling pathways or in negative regulation of viral genome replication. We mostly identified epigenetic signals at genes previously implicated in other SADs, for example MX1, PARP9, DDX60, or IFI44L, for which we also observed that MCTD patients exhibit higher DNA methylation variability compared with controls, suggesting that these sites might be involved in plastic immune responses that are relevant to the disease. Through methylation quantitative trait locus (meQTL) analysis we identified widespread local genetic effects influencing DNA methylation variability at MCTD-associated sites. Interestingly, for IRF7, IFI44 genes, and the HLA region we have evidence that they could be exerting a genetic risk on MCTD mediated through DNA methylation changes. Comparison of MCTD-associated epigenome with patients diagnosed with SLE, or Sjögren's Syndrome, reveals a common interferon-related epigenetic signature, however we find substantial epigenetic differences when compared with patients diagnosed with rheumatoid arthritis and systemic sclerosis. Furthermore, we show that MCTD-associated CpGs are potential epigenetic biomarkers with high diagnostic value. Our study serves to reveal new genes and pathways involved in MCTD, to illustrate the important role of epigenetic modifications in MCTD pathology, in mediating the interaction between different genetic and environmental MCTD risk factors, and as potential biomarkers of SADs.

Disease evolution in mixed connective tissue disease: results from a long-term nationwide prospective cohort study

Background

The phenotypic stability of mixed connective tissue disease (MCTD) is not clear, and knowledge about disease activity and remission is scarce. We aimed to establish the occurrence of evolution from MCTD to another defined rheumatic condition, and the prevalence and durability of remission after long-term observation.

Methods

In this large population-based prospective observational MCTD cohort study (N = 118), disease conversion was defined by the development of new auto-antibodies and clinical features compliant with another well-defined rheumatic condition. Remission was defined by a combination of systemic lupus erythematosus disease activity index 2000 (SLEDAI-2 K) of 0 and European League Against Rheumatism scleroderma trials and research (EUSTAR) activity index <2.5. Predictors of phenotypic stability and disease remission were assessed by logistic regression.

Results

Among 118 patients, 14 (12%) developed another well-defined rheumatic condition other than MCTD after mean disease duration of 17 (SD 9) years. Puffy hands predicted a stable MCTD phenotype in univariable regression analysis (OR 7, CI 2–27, P = .010). Disease activity defined by SLEDAI-2 K, decreased gradually across the observation period and > 90% of patients had EUSTAR activity index <2.5. There were 13% patients in remission throughout the whole mean observation period of 7 (SD 2) years. The strongest predictor of remission was percentage of predicted higher forced vital capacity.

Conclusions

Our results strengthen the view of MCTD as a relatively stable disease entity. Long-term remission in MCTD is not frequent; however, the low SLEDAI-2 K and EUSTAR scores during the observation period suggests that the disease runs a milder course than systemic lupus erythematosus and systemic sclerosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1494-7) contains supplementary material, which is available to authorized users.

Mixed connective tissue disease-enigma variations?

In 1972, Sharp et al. described a new autoimmune rheumatic disease that they called MCTD, characterized by overlapping features of SSc, SLE, PM/DM, high levels of anti-U1snRNP and low steroid requirements with good prognosis. MCTD was proposed as a distinct disease. However, soon after the original description, questions about the existence of such a syndrome as well as disputes over the features initially described began to surface. The conundrum of whether MCTD is a distinct disease entity remains controversial. We undertook a literature review, focusing on the articles reporting new data about MCTD published in the last decade, to determine whether any new observations help to answer the conundrum of MCTD. After reviewing recent data, we question whether the term MCTD is appropriately retained, preferring to use the term undifferentiated autoimmune rheumatic disease.

A 16-year Follow-up Case of Interstitial Pneumonia with Systemic Sclerosis-rheumatoid Arthritis Overlap Syndrome

Interstitial pneumonia is a common and major comorbidity affecting the prognosis of patients with systemic sclerosis (SSc). However, there are few reported cases of SSc-rheumatoid arthritis (RA) overlap-associated interstitial pneumonia. We herein report a case in which the clinical behavior and histopathology of interstitial pneumonia with SSc-RA overlap syndrome was followed over a long clinical course. When clinicians are deciding on the treatment strategy for patients with SSc-RA overlap syndrome-associated interstitial pneumonia, a pathological examination of a surgical lung biopsy may be useful.

Pediatric Mixed Connective Tissue Disease

Pediatric-onset mixed connective tissue disease is among the rare disease entities in pediatric rheumatology and includes features of arthritis, polymyositis/dermatomyositis, systemic lupus erythematosus, and systemic sclerosis. Accurate recognition and diagnosis of the disease is paramount to prevent long-term morbidity. Advances in the genetic and immunologic understanding of the factors involved in the etiopathogenesis provide an opportunity for improvements in prognostication and targeted therapy. The development of a multinational cohort of patients with mixed connective tissue disease would be invaluable to provide more updated data regarding the clinical presentation, to develop a standardized treatment approach, disease activity and outcome tools, and to provide data on long-term outcomes and comorbidities.

Progress in understanding the diagnostic and pathogenic role of autoantibodies associated with systemic sclerosis

PURPOSE OF REVIEW

At the time of diagnosis, systemic sclerosis (SSc) is often well established with significant irreversible tissue and organ damage. Definitions of 'early SSc' have been proposed, which include the presence of SSc-associated autoantibodies. In addition, functional autoantibodies that are believed to be involved in SSc pathogenesis need to be considered. In this review, recent advances in the diagnostic utility and pathogenic role of autoantibodies in early SSc are summarized. Moreover, we propose a clinical care pathway illustrating how autoantibody testing along with key clinical features can be used to make an earlier diagnosis of SSc.

RECENT FINDINGS

Recent evidence has helped to develop a clearer understanding of the natural history, early clinical features, and autoantibodies that are predictors of SSc. The role of functional autoantibodies is leading to innovative approaches to evidence-based interventions and therapies that are based on mechanisms of disease.

SUMMARY

Despite substantial advances, the high morbidity and mortality that currently characterizes SSc can largely be attributed to a delay in diagnosis, gaps in our understanding of the role of autoantibodies in early disease, and limited effective therapeutic options. An early and accurate diagnosis of SSc and use of autoantibody testing embedded in evidence-based clinical care pathways will help improve SSc-associated clinical outcomes and healthcare expenditures.

Epidemiology of Mixed Connective Tissue Disease, 1985-2014: A Population-Based Study

OBJECTIVE

To characterize the epidemiology of mixed connective tissue disease (MCTD) from 1983 to 2014.

METHODS

An inception cohort of patients with incident MCTD in 1985-2014 in Olmsted County, Minnesota was identified based on comprehensive individual medical record review. Diagnosis of MCTD required fulfillment of at least 1 of the 4 widely accepted diagnostic criteria without fulfillment of classification criteria for other connective tissue diseases. Data were collected on demographic characteristics, clinical presentation, laboratory investigations, and mortality.

RESULTS

A total of 50 incident cases of MCTD were identified (mean age 48.1 years and 84% were female). The annual incidence of MCTD was 1.9 per 100,000 population. Raynaud's phenomenon was the most common initial symptoms (50%), followed by arthralgia (30%) and swollen hands (16%). The diagnosis was frequently delayed with the median time from first symptom to fulfillment of criteria of 3.6 years. At fulfillment of criteria, arthralgia was the most prevalent manifestation (86%), followed by Raynaud's phenomenon (80%), swollen hands (64%), leukopenia/lymphopenia (44%), and heartburn (38%). Evolution to other connective tissue occurred infrequently with a 10-year rate of evolution of 8.5% and 6.3% for systemic lupus erythematosus and systemic sclerosis, respectively. The overall mortality was not different from the general population with a standardized mortality ratio of 1.1 (95% confidence interval 0.4-2.6).

CONCLUSION

This study was the first population-based study of MCTD to provide a complete picture of epidemiology and clinical characteristics of MCTD. MCTD occurred in about 2 persons per 100,000 per year. Evolution to other connective diseases occurred infrequently and the mortality was not affected.

Idiopathic inflammatory myopathies and the lung

Idiopathic inflammatory myositis (IIM) is a group of rare connective tissue diseases (CTDs) characterised by muscular and extramuscular signs, in which lung involvement is a challenging issue. Interstitial lung disease (ILD) is the hallmark of pulmonary involvement in IIM, and causes morbidity and mortality, resulting in an estimated excess mortality of 50% in some series. Except for inclusion body myositis, these extrapulmonary disorders are associated with the general and visceral involvement frequently found in other CTDs including fever, Raynaud's phenomenon, arthralgia, nonspecific cutaneous modifications and ILD, for which the prevalence is estimated to be up to 65%. Substantial heterogeneity exists within the spectrum of IIMs, and each condition is associated with various frequencies and subtypes of pulmonary involvement. This heterogeneity is partly related to the presence of various autoantibodies encompassing anti-synthetase, anti-MDA5 and anti-PM/Scl. ILD is present in all subsets of IIM including juvenile myositis, but is more frequent in dermatomyositis and overlap myositis. IIM can also be associated with other presentations of respiratory involvement, namely pulmonary arterial hypertension, pleural disease, infections, drug-induced toxicity, malignancy and respiratory muscle weakness. Here, we critically review the current knowledge about adult and juvenile myositis-associated lung disease with a detailed description of therapeutics for chronic and rapidly progressive ILD.

Cutaneous manifestations of mixed connective tissue disease: study from a tertiary care hospital in eastern India

Context:

Mixed connective tissue disorder is an uncommon disease. Some scientists are reluctant to recognize it as a separate entity. Some others have defined this ailment. Cutaneous features of this condition are unique. Researchers from India have described these features to relate to those described in the studies from other parts of the globe.

Aims:

This study aims to delineate the skin manifestations of clearly defined mixed connective tissue disease (MCTD) patients, to compare them with those established as overlap syndrome, and to relate them with studies from other parts of the globe.

Settings and Design:

Successive patients who fulfilled the specific criteria for MCTD presenting in the skin outpatient department of a tertiary care hospital in eastern India were clinically examined from 2009 for 3 years.

Materials and Methods:

The number of participants was 23 and the dermatological features of these were compared with 22 patients with overlap syndrome. The antibody to uridine-rich U1 ribonucleoprotein was measured for all patients.

Statistical Analysis Used:

SPSS (Version 17) and MedCalc (Version 11.6).

Results:

The Male: Female ratio among the MCTD patients was 1:6.67 and that of the overlap syndrome was 1:10. Twenty patients of the MCTD group presented with synovitis as against only seven in the overlap group. Raynaud's phenomenon was present in some of the subjects. Puffy fingers were rare in our study. Facial numbness was reported by four of those suffering from MCTD. Antinuclear antibody (ANA) was essentially of a speckled pattern in this disease

Conclusions:

Cutaneous indicators of MCTD are distinct from overlap syndrome. Knowledge of these manifestations prevalent in a region may lead to early diagnosis of the disease.

New autoantibodies in early rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease causing articular cartilage and bone destruction. Since irreversible joint destruction can be prevented by intervention at the early stages of disease, early diagnosis of RA is important. In this study, we identified new autoantibodies in the sera of patients with early (less than one year) RA.

METHODS

We screened the sera of 20 RA patients with disease duration less than one year, 19 RA patients with disease duration more than five years and 23 controls on 8,268 human protein arrays. We confirmed the validity of protein array detection by ELISA assays. We then performed epitope mapping with overlapping 15-mers to analyze RA sera reactivity.

RESULTS

WIBG (within BGCN homolog (Drosophila)), GABARAPL2 (GABA(A) receptor associated protein like 2) and ZNF706 (zinc finger protein 706) proteins are preferentially recognized by autoantibodies from early RA patients. Of interest, autoantibodies to WIBG are very specific for early RA. Indeed, 33% of early RA patients' sera recognize WIBG versus 5% of RA patients with disease duration more than 5 years and 2% of controls. We identified three linear peptides on WIBG GABARAPL2 and ZNF706 that are preferentially recognized by sera of early RA patients.

CONCLUSIONS

We identified new autoantibodies associated with RA with disease duration less than one year. These autoantibodies could be used as diagnosis markers in RA patients.

Isolated central nervous system vasculitis associated with antiribonuclear protein antibody

We describe the case of a young woman who was referred to a tertiary care center with unexplained subacute progressive encephalopathy preceded by long-standing severe headaches. Her extensive workup was remarkable for abnormal intracranial angiography suggestive of small- and medium-vessel vasculitis, persistently elevated protein in the cerebrospinal fluid and persistently high titers of antiribonuclear protein antibody. The patient showed a modest response to intravenous high-dose steroids. We propose that the patient's neurologic disease is secondary to immune-mediated central nervous system vasculitis, possibly as an initial manifestation of mixed connective tissue disease.

Interstitial lung disease associated with anti-PM/Scl or anti-aminoacyl-tRNA synthetase autoantibodies: a similar condition?

OBJECTIVE

To compare anti-PM/Scl autoantibody-associated interstitial lung disease (ILD) with anti-aminoacyl-tRNA synthetases (anti-ARS) autoantibody-associated ILD.

METHODS

We retrospectively studied 21 patients with ILD from a department of respiratory medicine, including 9 with anti-PM/Scl autoantibodies (6 women, median age 55 yrs, followup 5.5 yrs) and 12 with anti-ARS autoantibodies (6 women, median age 59 yrs, followup 2.3 yrs).

RESULTS

Pulmonary manifestations in patients with anti-PM/Scl autoantibody-associated ILD usually followed the extrapulmonary manifestations of the connective tissue disease (CTD) (7/9 cases). The predominant imaging features on initial high resolution computed tomography were ground-glass attenuation and reticular opacities, and mainly suggested nonspecific interstitial pneumonia in both groups. CTD was classified as dermatomyositis (DM; 2), undifferentiated CTD (2), cutaneous limited systemic sclerosis (2), rheumatoid arthritis (RA; 1), and overlap syndrome (1) in the anti-PM/Scl group; and polymyositis (4), undifferentiated CTD (5), DM (1), amyopathic DM (1), and RA (1) in the anti-ARS group. Frequencies of arthralgia, Raynaud phenomenon, cutaneous rash, and mechanic's hands were comparable in both groups. Myalgia or muscle weakness was present in 0/9 PM/Scl and 5/12 ARS patients (p < 0.05). More than 1 autoantibody was present in 11 patients. ILD worsened despite treatment in 4 patients with anti-PM/Scl autoantibodies and 2 with anti-ARS autoantibodies, and included 1 death.

CONCLUSION

Anti-PM/Scl and anti-ARS antibodies are associated with similar clinical manifestations, with the exception only of more overt myositis in the latter, therefore challenging the clinical specificity of the antisynthetase syndrome.

A case of mixed connective tissue disease complicated with hypertrophic obstructive cardiomyopathy

A 54-year-old female was diagnosed as mixed connective tissue disease (MCTD) complicated with secondary Sjögren's syndrome. Although she had no dyspnea on exertion, the chest X-ray showed cardiomegaly with interstitial pneumonia. The echocardiogram demonstrated asymmetric hypertrophy of the interventricular septum. Diagnosis of hypertrophic obstructive cardiomyopathy (HOCM) was confirmed by left ventriculography and myocardial biopsy. She was treated with prednisolone, resulting in improvement of swollen hand, elevated muscle enzymes and interstitial pneumonia. A rare complication of HOCM with MCTD was described.

Mixed connective tissue disease: what is behind the curtain?

Although there is still an emotional debate over the existence of mixed connective tissue disease, the evidence from animal models suggests that anti-U1RNP antibodies, similar to other autoantibodies in other connective tissue diseases (such as antisynthetase, anticentromere, and antitopoisomerase), play a pathophysiological role in this disease. Despite an antiendothelial effect of anti-U1RNP antibodies, which is reminiscent of anticentromere antibodies, patients with high-titer autoantibodies to U1RNP in the absence of anti-Sm antibodies do not usually have or develop typical systemic sclerosis. Instead, their severe Raynaud's syndrome is commonly accompanied by arthritis, which can be erosive, and by swollen/puffy hands and myositis. Pulmonary arterial hypertension is the major life-threatening complication in these patients and regular screening for this condition is essential.

Does Mixed Connective Tissue Disease Exist? Yes

For patients who have combined features of rheumatoid arthritis, the limited cutaneous form of systemic sclerosis, and inflammatory myopathies, the concept of mixed connective tissue disease (MCTD) often helps to predict and diagnose organ problems and to educate the patient accordingly. With high titer IgG antibodies to U1 ribonucleoprotein (U1-snRNP), this concept is supported by a specific serologic marker, and autoantibodies to U1-snRNP and to heterogeneous nuclear ribonucleoprotein (hnRNP)-A2 display MCTD specificity with regard to the recognized epitopes. In addition, the association of MCTD with HLA-DR4 distinguishes it from systemic erythematosus lupus and systemic sclerosis, and speaks to its being a disease entity, rather than a mixture of yet undifferentiated collagen vascular diseases. The authors believe that the concept is useful in daily practice and accurate in the idea that MCTD constitutes a disease entity of its own.

Autoantibodies in the Pathogenesis of Mixed Connective Tissue Disease

Antibodies to U1-RNP are part of the clinical definition of mixed connective tissue disease (MCTD). These antibodies and other well-defined antibodies tend to arise together in affected patients. Although still speculative, hypotheses that link U1-RNP antibodies to the development of autoimmunity in MCTD and that associate U1-RNP antibodies with mechanisms of tissue injury in MCTD have emerged and are being tested. Salient features of these hypotheses include: (1) an antigen-driven response that is due to impaired clearance of potentially immunogenic self-antigens, (2) inadequate B- and T-cell tolerance to RNP autoantigens, and (3) immunogenic properties of the RNA component of targeted ribonucleoproteins. Further studies are needed to establish whether anti-RNP antibodies have prognostic importance that is relevant to practicing clinicians.

Mixed Connective Tissue Disease: Still Crazy After All These Years

Mixed connective tissue disease (MCTD) remains a controversial diagnosis. The classification criteria have changed significantly from the original description by Sharp and colleagues in 1972 after follow-up of the original and other MCTD patients. In this article we review the clinical, serologic, and genetic studies of MCTD published in the last 10 years and ask if this term is appropriate.

MCTD - Mixed Connective Tissue Disease. MCTD - Mixed Connective Tissue Disease

Mixed connective tissue disease is a disease entity characterized by overlapping symptoms of lupus erythematosus (LE), systemic sclerosis (SSc), polymyositis/dermatomyositis (PM/DM) and rheumatoid arthritis (RA). Diagnostic criteria include high titers of antibodies against U1RNP as well as the presence of at least 3 of 5 of the following clinical features: edema of hands, synovitis, myositis, Raynaud phenomenon and acroscierosis. In terms of the pathogenesis, genetic as well as infectious (viral) factors appear to play a role. The acceptance of MCTD as a distinct disease entity is controversial. Terms such as "undifferentiated connective tissue disease" or "overlapping syndromes" are not helpful. One-quarter of MCTD patients transform into LE, while one-third progress to SSc. Therapeutic recommendations are glucocorticoids in combination with immunosuppressive agents and endothelin receptor antagonists. Double blind studies are not available. The prognosis is relatively good. Causes of death include pulmonary hypertension, infections and both pulmonary and cardiac failure.

Enfermedad mixta del tejido conjuntivo, conectivopatía indiferenciada y síndromes de superposición

Mixed connective tissue disease (MCTD), undifferentiated connective tissue disease and overlap syndromes are autoimmune systemic diseases that must be differentiated. Antibodies against the U1-ribonucleoprotein complex --spliceosome-- allows the diagnosis of mixed connective tissue disease. Links between the immunologic and clinical phenomena are emerging. Longitudinal studies of patients with MCTD highlight the impact of pulmonary hypertension and contribute to define the disease. Immunogenetic studies hold MCTD as an independent disease.

MICA4/HLA-DRB1*04/TNF1 haplotype is associated with mixed connective tissue disease in Swedish patients

In order to investigate major histocompatibility complex (MHC) class I chain-related gene A (MICA), tumor necrosis factor (TNFa), -308TNFA, and human leukocyte antigen (HLA-DR/DQ) polymorphisms in mixed connective tissue disease (MCTD), we analyzed 24 patients and 229 healthy controls from Sweden. MICA and TNFa typing was performed by polymerase chain reaction (PCR) and genotyping. HLA-DR and -DQ were genotyped using PCR-sequence specific primers (PCR-SSP) and PCR-sequence-specific oligonucleotide probe (PCR-SSOP), respectively. For analysis of -308TNFA polymorphisms we performed PCR with restriction endonuclease enzymes. We found that the MICA5.1-5.1 genotype was positively associated with MCTD. Shared epitope genes (DRB1*01 and DRB1*04) were also significantly positively associated with MCTD. Polymorphism of -308TNFA was not differently distributed in MCTD patients compared with controls. Furthermore, we demonstrated that frequencies of three estimated haplotypes were increased in MCTD patients compared with controls. Interestingly, the haplotype with MICA allele 4 together with DRB1*04 and TNF1 alleles gives the most specific pattern for MCTD patients compared with controls. Our study demonstrates a clear contribution of HLA loci in susceptibility to MCTD in the Swedish population. Susceptibility to MCTD may be linked to the MICA4/HLA-DRB1*04/TNF1 haplotype and MICA 5.1-5.1 genotype. Mixed connective tissue disease was also associated with shared epitope genes, which in RA has been associated with a more severe disease. Whether these genotypes affect the clinical phenotype of MCTD needs to be determined.

Mixed connective tissue disease: overlap syndromes

Since the original description of mixed connective tissue disease (MCTD) as an apparently unique syndrome by Sharp and co-workers, the concept of MCTD has been highly controversial. In this chapter, a quarter of a decade later, we examine the evidence that MCTD is a distinctive entity rather than a haphazard association of clinical and serological features and that the presence of high titres of autoantibodies to UIRNP influences the expression of connective tissue disease in ways that are relevant to prognosis and treatment. Results of longterm clinical studies are presented, which show that the clinical phenotype of MCTD is robust and can be defined by classification criteria that show reasonable sensitivity and specificity. In addition, the chapter addresses the results of immunogenetic and serological studies that demonstrate that MCTD is quite distinctive from systemic lupus erythematosus and systemic sclerosis. Indeed, there is good evidence that the clinical and serological features of MCTD are not just a haphazard association but that these patients represent a distinctive subset of connective tissue disease in which the specific autoimmune response is relevant to clinical expression and to understanding the underlying pathogenesis.

Unclassified or undifferentiated connective tissue disease

This chapter deals primarily with the evidence available regarding the use of the term unclassified or undifferentiated connective tissue disorders (CTDs) to refer to patients with manifestations suggestive, but not diagnostic, of either defined CTDs, a well-defined overlap syndrome (manifestations and criteria for two or more CTDs), or mixed CTD (MCTD). Possible outcomes for these patients include remaining undifferentiated, differentiating into a defined CTD or going into remission. MCTD and atypical CTD (term used by the parties involved in the 'Silicone breast implant' controversy) are only briefly discussed.

Scleroderma overlap syndromes

The most common scleroderma overlap syndromes are mixed connective tissue disease (MCTD), scleromyositis and synthetase syndrome. There is controversy concerning MCTD as a separate entity due to heterogeneous clinical manifestations, not infrequent transformation into definite CTD and various classification criteria. Our study of 94 adult patients and 20 children, classified according to the criteria of Alarcon-Segovia, and especially a 5, 9-year follow-up showed transformation into SLE or SSc in over 20% of patients, less frequently than reported by others, whereas over half of the cases remained undifferentiated CTD. In several cases ARA criteria for both SSc and SLE were fulfilled, and there is no consensus whether such cases should be recognized as coexistence of both definite diseases or as MCTD. High titers of U1 RNP antibodies to 70 kD epitope were invariably present, whereas, by transformation into distinctive CTD there appeared, in addition, antibodies characteristic of these CTD. Of 108 cases positive for PM-Scl antibody, 83% were associated with scleromyositis. This scleroderma overlap syndrome differed from MCTD by coexistent features of dermatomyositis (myalgia, myositis, Gottron sign, heliotrope rash, calcinosis) with no component of SLE, characteristic of MCTD. The course was also chronic and rather benign, as in MCTD, and all cases responded to low or moderate doses of corticosteroids. A not infrequent complication was deforming arthritis of the hands. Our immunogenetic study showed an association of cases positive for PM-Scl antibody with HLA-DQA1x0501 alleles in 100% and with HLA-DRB1x0301 in 94% of cases. Synthetase syndrome, associated with anti-histidyl-tRNA synthetase antibodies, studied in 29 patients with myositis and interstitial lung disease (ILD), only in single cases had scleroderma-like features. These cases differed from SSc by acute onset with fever, and by response to moderate doses of corticosteroids. We also studied overlap of localized scleroderma with other CTD: 21 cases of progressive facial hemiatrophy and linear scleroderma, and 55 (39.5%) of atrophoderma Pasini-Pierini (APP) and morphea. As in other autoimmune disorders, two or more connective tissue diseases (CTD) may develop concurrently or sequentially in the same patient. In such overlap syndromes ARA criteria must be fulfilled for each of the disease, and the clinical presentation has features of both. However more frequently overlap syndromes only combine some manifestations of more than one CTD, and present a highly heterogeneous group of disorders with prevailing clinical features of SSc.

Recombinant cytomegalovirus glycoprotein gB (UL55) induces an autoantibody response to the U1-70 kDa small nuclear ribonucleoprotein

Human cytomegalovirus (CMV) infection can be life threatening in the immune compromised and is associated with congenital defects and / or mental retardation in the neonate. The demonstrated association between CMV infection and rheumatoid factor (RF) raised the possibility of an induction of an autoimmune response upon vaccination with a candidate CMV vaccine, glycoprotein gB (UL55). The antibody responses generated after injections of an adenovirus-gB construct (Ad-gB) were studied in autoimmune-prone (MRL/mpj) and normal (BALB.k, C3H, and BALB/c) mice. Enzyme-linked immunosorbent assay and immunoblot analyses were done to identify the autoantibodies produced following immunization. Immunization with Ad-gB induced a significant IgG anti-viral response in all strains tested (p < 0.0001) compared to phosphate-buffered saline or HeLa controls. Ad-gB induced a significant IgG autoantibody response (p > 0.005) to the U1-70 kDa spliceosome protein in both autoimmune and normal strains whereas immunization with recombinant human La/SS-B did not. Autoantibodies to U1-70 kDa are part of the anti-ribonucleoprotein response seen in systemic lupus erythematosus and mixed connective tissue disease. Low levels of IgG RF and anti-double-stranded DNA antibodies were also induced. This study raises concern that immunization with CMV gB in individuals genetically predisposed to autoimmunity could trigger the development or acceleration of an autoimmune disease.

Long-term outcome in mixed connective tissue disease: longitudinal clinical and serologic findings

OBJECTIVE

To determine the long-term clinical and immunologic outcomes in a well-characterized cohort of 47 patients with mixed connective tissue disease (MCTD), including reactivity with U small nuclear RNP (snRNP) polypeptides.

METHODS

Patients were followed up over a period of 3-29 years with immunogenetic and systematic clinical and serologic analysis. Sera were analyzed for reactivity with snRNP polypeptides U1-70 kd, A, C, B/B', and D, for anti-U1 RNA, and for anticardiolipin antibodies (aCL).

RESULTS

The typical core clinical features of MCTD tended to develop over time; features of inflammation as well as Raynaud's phenomenon and esophageal hypomotility diminished, while pulmonary hypertension, pulmonary dysfunction, and central nervous system disease persisted, following treatment. A favorable outcome was observed in 62% of patients; 38% had continued active disease or had died, with death associated with pulmonary hypertension and aCL. All patients had autoantibodies to the U1-70 kd polypeptide of snRNP, and most were positive for anti-U1 RNA. An orderly progression of intramolecular spreading of autoantibody reactivity against snRNP polypeptides was observed, as was the novel finding of "epitope contraction" followed by disappearance of anti-snRNP autoantibodies during prolonged remission.

CONCLUSION

These patients demonstrated the typical immunogenetic, clinical, and serologic findings of MCTD, and the condition rarely evolved into systemic lupus erythematosus or systemic sclerosis. The majority of patients had favorable outcomes, with pulmonary hypertension being the most frequent disease-associated cause of death. Intramolecular spreading of autoantibody reactivity against snRNP polypeptides was observed, followed by "epitope contraction" and ultimate disappearance of anti-snRNP autoantibodies during prolonged disease remission.

Long-term outcome in mixed connective tissue disease: longitudinal clinical and serologic findings

OBJECTIVE

To determine the long-term clinical and immunologic outcomes in a well-characterized cohort of 47 patients with mixed connective tissue disease (MCTD), including reactivity with U small nuclear RNP (snRNP) polypeptides.

METHODS

Patients were followed up over a period of 3-29 years with immunogenetic and systematic clinical and serologic analysis. Sera were analyzed for reactivity with snRNP polypeptides U1-70 kd, A, C, B/B', and D, for anti-U1 RNA, and for anticardiolipin antibodies (aCL).

RESULTS

The typical core clinical features of MCTD tended to develop over time; features of inflammation as well as Raynaud's phenomenon and esophageal hypomotility diminished, while pulmonary hypertension, pulmonary dysfunction, and central nervous system disease persisted, following treatment. A favorable outcome was observed in 62% of patients; 38% had continued active disease or had died, with death associated with pulmonary hypertension and aCL. All patients had autoantibodies to the U1-70 kd polypeptide of snRNP, and most were positive for anti-U1 RNA. An orderly progression of intramolecular spreading of autoantibody reactivity against snRNP polypeptides was observed, as was the novel finding of "epitope contraction" followed by disappearance of anti-snRNP autoantibodies during prolonged remission.

CONCLUSION

These patients demonstrated the typical immunogenetic, clinical, and serologic findings of MCTD, and the condition rarely evolved into systemic lupus erythematosus or systemic sclerosis. The majority of patients had favorable outcomes, with pulmonary hypertension being the most frequent disease-associated cause of death. Intramolecular spreading of autoantibody reactivity against snRNP polypeptides was observed, followed by "epitope contraction" and ultimate disappearance of anti-snRNP autoantibodies during prolonged disease remission.

Respiratory complications in mixed connective tissue disease

The term mixed connective tissue disease is used to identify the patients with combined clinical features of systemic lupus erythematosus, scleroderma or progressive systemic sclerosis, and polymyositis-dermatomyositis. A prerequisite for the diagnosis of mixed connective tissue disease is the presence, in the serum, of high titers of antibodies against uridine-rich RNA-small nuclear ribonucleoprotein (snRNP). Respiratory and nonrespiratory features of the disease follow those seen in systemic lupus erythematosus, scleroderma, or progressive systemic sclerosis, and polymyositis-dermatomyositis. Respiratory involvement is observed in 20% to 80% of patients. Major respiratory manifestations and their incidences described include interstitial pneumonitis and fibrosis (20% to 65%), pleural effusion (50%), pleurisy (20%), and pulmonary hypertension (10% to 45%). Other pulmonary features consist of pulmonary vasculitis, pulmonary thromboembolism, aspiration pneumonia, pulmonary hemorrhage, pulmonary nodules, pulmonary cysts, obstructive airways disease, mediastinal lymphadenopathy, pulmonary infections, hypoventilatory respiratory failure, and diaphragmatic dysfunction. Pulmonary hypertension is a serious complication; rapid deterioration and death have occurred in spite of corticosteroid and cytotoxic chemotherapy.

Course of mixed connective tissue disease in children

Mixed connective tissue disease (MCTD) was first reported 25 years ago. This report provides an assessment of the course of juvenile (J) MCTD in 224 patients available in the literature until 1996, including our own 33 patients. Most patients improved and remissions were observed in 3-5% (up to 27%). Among the long-term problems, a loss in joint function was seen in up to 29% of the cases, renal involvement in up to 47%, restrictive lung disease in up to 54% and gastrointestinal manifestations consisting of oesophageal dysmotility in up to 29%. Cerebral involvement was rare but severe. Cardiovascular problems observed include cardiomyopathy, myopericarditis and pulmonary hypertension. Among other long-term problems were Raynaud's phenomenon and scleroderma-like skin changes in up to 86% of the patients. Seventeen of the 224 patients had died (7.6%) because of sepsis or infection (7), cerebral complications (3), heart failure (2), pulmonary hypertension (2), renal failure (2) or gastrointestinal bleeding (1). The mortality rate of JMCTD seems to be in the same range as that of juvenile systemic lupus erythematosus, dermatomyositis and scleroderma. When compared with the other connective tissue diseases, however, mainly minor long-term problems are seen in the surviving patients.

Clinical correlations with HLA type in Japanese patients with connective tissue disease and anti-U1 small nuclear RNP antibodies

OBJECTIVE

To elucidate the roles of HLA genes in the clinical presentation of patients with connective tissue disease and serum anti-U1 small nuclear RNP antibody.

METHODS

HLA class I antigens and HLA class II alleles were determined in 43 Japanese patients with anti-U1 RNP antibody alone, by microcytotoxicity testing and DNA typing, respectively. Prospectively recorded clinical and laboratory features were analyzed in relation to HLA class I and class II types.

RESULTS

DQB1*0303 was associated with lupus-related symptoms including fever, malar rash, oral ulcers, hypocomplementemia, and high-titer anti-double-stranded DNA antibody. Other HLA-clinical associations included DR2 with pleuritis, DR4 with hand swelling, and DRB1*0405 with arthritis.

CONCLUSION

These HLA-clinical associations explain, in part, the heterogeneous clinical presentation in patients with anti-U1 RNP antibody.