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.

Application of SLICC classification criteria in undifferentiated connective tissue disease and evolution in systemic lupus erythematosus: analysis of a large monocentric cohort with a long-term follow-up.

Objectives The objectives of this study were to analyse the performance of the Systemic Lupus International Collaborating Clinics (SLICC) 2012 classification criteria for systemic lupus erythematosus (SLE) in a large cohort of undifferentiated connective tissue disease (UCTD) population at onset of the disease and during a long-term follow-up of 15 years (1999-2013) and to evaluate the transition from UCTD to SLE, according to American College of Rheumatology (ACR) 1997 and SLICC 2012 classification criteria. Methods A cohort of patients who met the classification criteria proposed by Mosca et al. for UCTD, were analysed. The SLICC 2012 classification criteria for SLE were retrospectively applied to each patient at the time of the diagnosis (T0) and also periodically re-applied and compared to ACR 1997 criteria at three different time points in the follow-up. Results 329 patients were enrolled. According to inclusion criteria at T0 no patient met the SLE/ACR criteria, whilst, retrospectively applying the SLE/SLICC criteria, 44 patients already satisfied this set of criteria for SLE. During the follow-up 23 new patients reached the SLE/SLICC criteria and 14 patients met the ACR criteria with a stable rate of progression to SLE over time. Acute or subacute skin rash, antiphospholipid antibody (aPL) positivity and serositis were the variables correlated to the evolution to SLE. Conclusions In our UCTD population, the application of SLICC classification criteria for SLE at disease onset allowed identification of a proportion of otherwise missed SLE cases; during follow-up, and compared with ACR criteria, SLICC criteria expanded the number of patients classifiable as SLE otherwise classified as UCTD.

Can SLE classification rules be effectively applied to diagnose unclear SLE cases?

Objective The objective of this paper is to develop novel classification criteria to distinguish between unclear systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) cases. Methods A total of 205 variables from 111 SLE and 55 MCTD patients were evaluated to uncover unique molecular and clinical markers for each disease. Binomial logistic regressions (BLRs) were performed on currently used SLE and MCTD classification criteria sets to obtain six reduced models with power to discriminate between unclear SLE and MCTD patients that were confirmed by receiving operating characteristic (ROC) curve. Decision trees were employed to delineate novel classification rules to discriminate between unclear SLE and MCTD patients. Results SLE and MCTD patients exhibited contrasting molecular markers and clinical manifestations. Furthermore, reduced models highlighted SLE patients exhibiting prevalence of skin rashes and renal disease while MCTD cases show dominance of myositis and muscle weakness. Additionally decision tree analyses revealed a novel classification rule tailored to differentiate unclear SLE and MCTD patients (Lu-vs-M) with an overall accuracy of 88%. Conclusions Validation of our novel proposed classification rule (Lu-vs-M) includes novel contrasting characteristics (calcinosis, CPK elevated and anti-IgM reactivity for U1-70K, U1A and U1C) between SLE and MCTD patients and showed a 33% improvement in distinguishing these disorders when compared to currently used classification criteria sets. Pending additional validation, our novel classification rule is a promising method to distinguish between patients with unclear SLE and MCTD diagnosis.

The diagnosis and classification of mixed connective tissue disease.

The term "mixed connective tissue disease" (MCTD) concerns a systemic autoimmune disease typified by overlapping features between two or more systemic autoimmune diseases and the presence of antibodies against the U1 small nuclear ribonucleoprotein autoantigen (U1snRNP). Since the first description of this condition in 1972, the understanding of clinical manifestations and long-term outcome of MCTD have significantly advanced. Polyarthritis, Raynaud's phenomenon, puffy fingers, lung involvement and esophageal dysmotility are the most frequently reported symptoms among the different cohorts during the course of the disease. Moreover, in recent years a growing interest has been focused on severe organ involvement such as pulmonary arterial hypertension and interstitial lung disease which can accrue during the long-term follow-up and can still significantly influence disease prognosis. Over the last years, significant advances have been made also in disease pathogenesis understanding and a central pathogenetic role of anti-U1RNP autoantibodies has clearly emerged. Although controversies on disease definition and classification still persist, MCTD identifies a group of patients in whom increased surveillance for specific manifestations and prognostic stratification became mandatory to improve patient's outcomes.

Distinct phenotypes in mixed connective tissue disease: subgroups and survival.

The aim of the present study was to assess the autoantibody profile, dominant clinical symptoms and cluster characteristics of different mixed connective tissue disease (MCTD phenotypes. Two-hundred-and-one patients with MCTD were followed-up longitudinally. Five clinical parameters, Raynaud's phenomenon, pulmonary artery hypertension (PAH), myositis, interstitial lung disease (ILD), erosive arthritis and five auto-antibodies besides anti-U1RNP, antiendothelial cell antibodies (AECA), anti-CCP, anti-cardiolipin (anti-CL), anti-SSA/SSB and IgM rheumatoid factor (RF) were selected for cluster analysis. The mean age of patients was 52.9 ± 12.4 years and the mean follow-up of the disease was 12.5 ± 7.2 years. Patients were classified into three cluster groups. Cluster 1 with 77 patients, cluster 2 with 79 patients and cluster 3 with 45 patients. In cluster 1 the prevalence of PAH (55.8%; p < 0.001), Raynaud's phenomenon (92.2%; p < 0.001) and livedo reticularis (24.6%, p < 0.001) was significantly greater than in cluster 2 and 3. In cluster 2, the incidence of ILD (98.7%; p < 0.001), myositis (77.2%; p < 0.001), and esophageal dysmotility (89.8%; p < 0.001) was significantly greater than that in cluster 1 and 3. In cluster 3, anti-CCP antibodies were present in 31 of 45 patients (68.8%) with erosions. Anti-CCP antibodies were present in 37 of 42 patients (88.0%) with erosions. PAH, angina, venous thrombosis was observed in cluster 1 and pulmonary fibrosis in cluster 2, musculosceletal damage, gastrointestinal symptoms and osteoporotic fractures were most frequent in cluster 3. Cumulative survival assessment indicated cluster 1 patients having the worst prognosis. Cluster analysis is valuable to differentiate among various subsets of MCTD and useful prognostic factor regarding the disease course.

An external validation study of a classification of mixed connective tissue disease and systemic lupus erythematosus patients.

Mixed Connective Tissue Disease (MCTD) and Systemic Lupus Erythematosus (SLE) are autoimmune rheumatic diseases that are difficult for physicians to diagnose and to distinguish for a variety of reasons. The correct classification of these two diseases is a crucial issue for clinicians who treat autoimmune rheumatic diseases. In prior research, medical risk factors represented by instrument or laboratory measures and physician judgments (12 key features for MCTD and 12 key features for SLE) were parameterized with a one parameter logistic function in a Rasch model. Those results identified separate diagnostic dimensions for MCTD and SLE. This procedure was replicated in the present research with a sample of largely African American and Hispanic patients. Results verified separate dimensions for MCTD and SLE, which suggests MCTD is a separate disease from SLE.

Immune pathogenesis of Mixed Connective Tissue Disease: a short analytical review.

Mixed Connective Tissue Disease (MCTD) was first described 35 years ago by Gordon C. Sharp and his colleagues. In the ensuing decades, a clearer understanding of the clinical and serologic features of MCTD has emerged. Classification criteria now exist to define MCTD for study purposes, the long-term outcome of the disease has been established, and novel genetic associations within the major histocompatibility complex on chromosome 6 and select regions on chromosome 3 have been identified. Studies on immune pathogenesis have made substantial progress in advancing our understanding of MCTD. In MCTD, there is a complex interaction of the innate and adaptive immune system that culminates in autoimmune disease. Antigenic structural modification occurring during apoptosis or other modifications of self antigens leads to an autoantigen driven immune process with innate immune activation, immunoglobulin G autoantibody production directed against select components of the spliceosome, B lymphocyte activation, and CD4 and CD8 T lymphocyte participation.

A Rasch analysis for classification of systemic lupus erythematosus and mixed connective tissue disease.

The classification of rheumatic diseases is challenging because these diseases have protean and frequently overlapping clinical and laboratory manifestations. This problem is typified by the difficulty of classification and differentiation of two prototypic multi-system autoimmune diseases, Systemic Lupus Erythematosus (SLE) and Mixed Connective Tissue Disease (MCTD). The researchers submitted medical risk factor data represented by instrument or laboratory measures and physician judgments (12 key features for SLE) from 43 patients diagnosed with SLE and 12 key features for MCTD from 51 patients diagnosed with MCTD to the WINSTEPS Rasch analysis program. Using Rasch model parameterization, and fit and residuals analyses, the researchers identified separate dimensions for MCTD and SLE, thereby lending support to the position that MCTD is its own separate disease, distinct from SLE.

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.

Performance of the 2013 American College of Rheumatology/European League Against Rheumatism Classification Criteria for Systemic Sclerosis (SSc) in large, well-defined cohorts of SSc and mixed connective tissue disease.

OBJECTIVE: To assess the 2013 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) Classification Criteria for Systemic Sclerosis (SSc) on defined subgroups of SSc and in mixed connective tissue disease (MCTD) as an SSc-related disease. METHODS: The 2013 ACR/EULAR criteria were assessed in 425 consecutive patients suspected to have SSc and seen at Oslo University Hospital, and in the nationwide Norwegian MCTD cohort (n = 178). In the SSc group, 239/425 patients had disease duration < 3 years (in 82 of these, duration was < 1 yr). Patients were subgrouped as limited SSc (n = 294), diffuse SSc (n = 97), SSc sine scleroderma (n = 10), and early SSc (prescleroderma; n = 24). Item data were complete, except nailfold capillaroscopy and telangiectasia results, missing in the MCTD cohort. RESULTS: The 2013 ACR/EULAR SSc criteria were met by 409/425 patients (96%) in the SSc group. For comparison, only 75% (293/391) met the 1980 ACR SSc classification criteria. All the novel items in the 2013 ACR/EULAR criteria were frequent in the SSc cohort. Considering that there were missing data on 2 items, 10% (18/178) of the MCTD cohort met the 2013 ACR/EULAR criteria, giving an estimated specificity of 90% toward this SSc-like disorder. CONCLUSION: In our large and representative group of consecutive patients with SSc, the 2013 ACR/EULAR SSc criteria were more sensitive than the ACR 1980 criteria. However, the new criteria did not completely segregate SSc from MCTD, making specificity a potential issue.

Undifferentiated, overlapping, and mixed connective tissue diseases.

Undifferentiated connective tissue disease (UCTD) is a term used by many rheumatologists to define a group of diffuse connective tissue disorders that lack definitive characteristics of any particular well-defined disorder. Overlapping connective tissue disease is often used interchangeably with UCTD but they both refer to diseases that are in evolution before all the characteristic clinical and laboratory symptoms are manifested. However, the clinical features of some of the overlapping connective tissue diseases appear to be better defined. The classical one is mixed connective tissue disease, where features of systemic lupus erythematosus, progressive systemic sclerosis, and polymyositis may exist together with a positive anti-extractable nuclear antibody and high titers of anti-ribonuclear protein antibody. This review attempts to clarify the confusion between these terms. The problems in the clinical and laboratory diagnosis of common connective tissue diseases that coexist are addressed and treatment options discussed. The long-term implications of making a diagnosis of a definitive connective tissue disease before all the required criteria are met should be kept in mind because the patient may never develop the disease and yet be subjected to psychological, social, and economic hardships.

Is MCTD a distinct entity? Comparison of clinical and laboratory findings in MCTD, SLE, PSS, and RA patients.

Eighteen patients diagnosed as suffering from MCTD were reexamined during follow-up (mean duration 4.6 years). The clinical features of these patients were compared with those of 19 patients with systemic lupus erythematosus (SLE), 11 with progressive systemic sclerosis (PSS) and 22 with rheumatoid arthritis (RA). Considerable overlapping of abnormal features was found between MCTD and the other syndromes. At the end of the follow-up period, 70 per cent of the cases initially diagnosed as MCTD evolved to a more classical connective tissue disease, i.e., either PSS or SLE. Generally, however, the clinical evolution of the individual MCTD patient was not predictable. Abnormal aortic valve calcifications were found in the MCTD group. Four of the 18 MCTD patients were anti-RNP negative at reexamination. There was a tendency for HLA antigens B7 and B8 to be increased in the MCTD group, but this difference was not statistically significant. Three MCTD patients died before they could be reexamined (two of them from pulmonary hypertension with proliferative endarteritis of the lung vessels and one from septicaemia and multiple cerebral infarctions.

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.

Mixed connective tissue disease.

Mixed connective tissue disease deserves to be a distinct disease entity due to the persistent citation of this disease in the literature since the original description by Sharp in 1972, in spite of the presence of several criticisms against the independency of this disease. The characteristic features of mixed connective tissue disease are: 1) the presence of anti-U1snRNP antibody with high titers in sera, 2) an increased frequency of HLA-DR4 in the leukocytes, and 3) death due to pulmonary hypertension.

[Sharp's syndrome. Clinical, immunological and nosographic aspects]. / La sindrome di Sharp. Studio clinico, immunologico e nosografico.

LE cells, ds-DNA antibodies (radioimmunoassay), antinuclear antibodies (ANA) by indirect immunofluorescence (IFI) and anti-ENA antibodies have been sought in 150 clinical cases observed over a 5-year period in the Rheumatology Division of Bari University. For the latter, three parallel techniques were adopted on each serum, each completed by RNA-sensitivity assay for the demonstration of anti-RNP, i.e. IFI, passive haemoagglutination (PHA) and controimmunoelectrophoresis (CIE). The series included systemic lupus erythematodes (SLE), 30 cases; rheumatoid arthritis (RA), 30 cases; progressive systemic sclerosis (PSS), 12 cases; unclassified connective tissue disease (UCTD), 8 cases; mixed connective tissue disease (MCTD), 7 cases; Sjögren's syndrome (SS), 4 cases; dermatomyositis (DM), 3 cases; overlap syndromes (PSS-SLE, SS-SLE), 2 cases; rheumatological and internal miscellanea, 54 cases, LE cells and ds-DNA antibodies were found exclusively in SLE; the anti-ENA were found in various groups of diseases, while the anti-RNP were only demonstrated in the 7 MCTD and in some SLE. Of the three techniques for demonstrating anti-ENA, the PHA proved most sensitive and CIE most specific, whereas IFI was considered most suitable for clinical screening. The clinical aspects of the 7 MCTD faithfully followed the disease picture described by Sharp, but some overlap-syndromes and the unclassified connective tissue diseases did not present anti-RNP. It is also pointed out that nephropathy is not rare in MCTD and that the clinical course of the disease is not always benign. To conclude, it is considered that MCTD merits nosographic autonomy, but further investigations are recommended for more exact nosographical typing of connective tissue diseases.

[Undifferentiated, overlapping and mixed connective tissue diseases]. / 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.

[Clinical observations in mixed connective tissue disease]. / Klinikai megfigyelések kevert kötöszöveti betegségben.

The authors report their observations gathered by follow-up studies of many years duration on 67 patients suffering from mixed connective tissue disease. The period preceding the overt disease, its duration and its characteristic symptoms were examined. Concerning the severity of the clinical course, the authors distinguished between a less and a more severe form of the disease. Organ specific manifestations occurring in the two types of the disorder, the number of active phases per year, therapeutic tools and the prognosis were analysed. The authors assume that the more severe form of the disease may have some traits resembling those of systemic lupus erythematosus, but in the meantime, in the less severe type of the disease some features shared by rheumatic disorders can be found.

"To be or not to be," ten years after: evidence for mixed connective tissue disease as a distinct entity.

OBJECTIVES: To determine if mixed connective tissue disease (MCTD) can be considered an independent clinical entity, to compare 3 different classification criteria for MCTD (Kasukawa, Alarcón-Segovia, and Sharp), and to define predictors (clinical features and autoantibodies) of potential evolution toward other connective tissue diseases (CTDs). METHODS: One hundred sixty-one MCTD patients were evaluated retrospectively at the diagnosis and in 2008. They were classified, at the diagnosis, according to the 3 classification criteria of MCTD (Sharp, Alarcón-Segovia, and Kasukawa) and reclassified in 2008 according to their evolution. Statistical analyses were performed to find out predictors (clinical features and autoantibodies) of evolution into other CTDs. RESULTS: After a mean of 7.9 years of disease, 57.9% of patients still satisfied MCTD classification criteria of Kasukawa; 17.3% evolved into systemic sclerosis, 9.1% into systemic lupus erythematosus, 2.5% into rheumatoid arthritis, 11.5% was reclassified as affected by undifferentiated connective tissue disease, and 1.7% as suffering from overlap syndrome. Kasukawa's criteria were more sensitive (75%) in comparison to those of Alarcón-Segovia (73%) and Sharp (42%). The presence of anti-DNA antibodies (P = 0.012) was associated with evolution into systemic lupus erythematosus; hypomotility or dilation of esophagus (P < 0.001); and sclerodactyly (P = 0.034) with evolution into systemic sclerosis. CONCLUSIONS: MCTD is a distinct clinical entity but it is evident that a subgroup of patients may evolve into another CTD during disease progression. Initial clinical features and autoantibodies can be useful to predict disease evolution.