Mixed connective tissue disease: overlap syndromes

The phenotype of mixed connective tissue disease patients having associated interstitial lung disease

OBJECTIVE

We aimed to compare two matched populations of patients with MTCD with and without associated ILD and to identify predictive factors for ILD progression and severity.

METHODS

This international multicenter retrospective study (14 tertiary hospitals), included MCTD patients who fulfilled at least one historical MCTD classification criteria. ILD was defined by the presence of typical chest high-resolution computed tomography (HRCT) abnormalities. Factors associated with ILD were assessed at baseline. Long-term progressive ILD was assessed in MCTD-ILD patients with multiple forced vital capacity (FVC) measurements.

RESULTS

300 patients with MCTD were included. Mean age at diagnosis was 39.7 ± 15.4 years and 191 (63.7%) were women. Mean follow-up was 7.8 ± 5.5 years. At baseline, we identified several factors associated with ILD presence: older age (p = 0.01), skin thickening (p = 0.03), upper gastro-intestinal (GI) symptoms (p<0.001), FVC <80% (p<0.0001), diffusing capacity for carbon monoxide <80% (p<0.0001), anti-topoisomerase antibodies (p = 0.01), SSA/Ro antibodies (p = 0.02), cryoglobulinemia (p = 0.04) and elevated C-reactive protein (p<0.001). Patients with MTCD-ILD were more likely to be treated with synthetic immunosuppressant agents (p<0.001) in particular mycophenolate mofetil (p = 0.03). Digital ulcers (DU) were identified as a risk factor for FVC decline >10%. During follow-up mortality was higher in the MTCD-ILD group (p<0.001).

CONCLUSION

In this large international cohort of patients with MTCD, we identified different factors associated with ILD. Our findings also provide evidence that MCTD-ILD patients have increased mortality and that DU are associated with progressive lung disease.

Antinuclear Antibodies in Systemic Sclerosis: an Update

Systemic sclerosis is an autoimmune disease characterized by fibrosis of skin and internal organs, vasculopathy, and dysregulation of immune system. A diagnostically important feature of immunological abnormalities in systemic sclerosis is the presence of circulating antinuclear antibodies, which may be detected in 90-95% of patients with either of the four main laboratory methods: immunofluorescence, enzyme-linked immunosorbent assay, immunodiffusion, and immunoblotting. There are several antinuclear antibodies specific for systemic sclerosis. These include antibodies against topoisomerase (anti-TOPO I), kinetochore proteins (ACA), RNA polymerase enzyme (anti-RNAP III), ribonuclear proteins (anti-U11/U12 RNP, anti-U1 RNP, anti-U3 RNP) and nucleolar antigens (anti-Th/To, anti-NOR 90, anti-Ku, antiRuvBL1/2, and anti-PM/Scl). Autoantibodies specific for systemic sclerosis have been linked to distinct clinical features. Therefore, detecting a particular antibody type is important in predicting a possible organ involvement and prognosis and may have an impact on monitoring and treatment.

Long-term clinical course and outcome of interstitial pneumonia with autoimmune features

BACKGROUND AND OBJECTIVE

Idiopathic interstitial pneumonia (IIP) with autoimmune features that does not fulfil connective tissue disease (CTD) criteria has been recently defined as interstitial pneumonia with autoimmune features (IPAF). However, its long-term clinical course and outcome are poorly understood.

METHODS

We included consecutive patients diagnosed with IIP (n = 586) or CTD-related interstitial lung disease (CTD-ILD, n = 149). Some patients with IIP were reclassified as IPAF based on recent guidelines.

RESULTS

The median follow-up period was 45 months. Among the IIP patients, 109 (18.6%) were reclassified as IPAF. Compared to the non-IPAF-IIP group, the IPAF group had slower diffusing capacity of the lung for carbon monoxide (DL_CO ) and total lung capacity declines, and more frequent CTD development during follow-up periods. The prognosis of the IPAF was better than that of the non-IPAF-IIP and similar to that of the CTD-ILD. IPAF was associated with better prognosis in the IIP cohort on univariate but not on multivariate analysis. Usual interstitial pneumonia (UIP) pattern, old age and low DL_CO independently predicted mortality in the IPAF group.

CONCLUSION

Compared to the non-IPAF-IIP group, the IPAF group had slower lung function declines and more frequent CTD development during follow-up. Although the prognosis of IPAF group was better than that of non-IPAF-IIP group and similar to that of CTD-ILD group, it showed poor prognosis in patients with old age, UIP pattern, and low DL_CO .

Cytokine Milieu in Undifferentiated Connective Tissue Disease: a Comprehensive Review

Undifferentiated connective tissue disease (UCTD) is a unique clinical entity, a potential forerunner of well-established systemic autoimmune/rheumatic diseases. UCTD is characterized by the presence of various clinical symptoms, as well as a diverse repertoire of autoantibodies, resembling systemic autoimmune diseases. Since approximately one third of these patients consequently transform into a full-blown systemic autoimmune/rheumatic disease, it is of major importance to assess pathogenic factors leading to this progression. In view of the fact that the serological and clinical picture of UCTD and systemic autoimmune diseases are very similar, it is assumed that analogous pathogenic factors perpetuate both disease entities. In systemic autoimmune conditions, a quantitative and qualitative impairment of regulatory T cells has been shown previously, and in parallel, a relative dominance of pro-inflammatory Th17 cells has been introduced. Moreover, the imbalance between regulatory and Th17 cells plays a pivotal role in the initiation and propagation of UCTD. Additionally, we depict a cytokine imbalance, which give raise to a biased T cell homeostasis from the UCTD phase throughout the fully developed systemic autoimmune disease stage. The levels of interleukin (IL)-6, IL-12, IL-17, IL-23, and interferon (IFN)-γ were pathologically increased with a parallel reduction of IL-10. We believe that the assessment of Th17/Treg cell ratio, as well as the simultaneous quantitation of cytokines may give a useful diagnostic tool at the early UCTD stage to identify patients with a higher chance of consecutive disease progression toward serious systemic autoimmune diseases. Moreover, the early targeted immunomodulating therapy in these patients may decelerate, or even stop this progression, before the development of serious autoimmune conditions with organ damage.

‘Concealing the Evidence’: The Importance of Appearance Concerns for Patients with Systemic Lupus Erythematosus

Outwardly visible signs associated with systemic lupus erythematosus (SLE) can include facial rashes, alopecia and weight gain. We sought to understand the concerns of SLE patients about their appearance and the recognition of this by healthcare professionals. Semi-structured interviews were carried out with 10 women aged 26-68 years diagnosed with SLE for one to 12 years. Data were analysed with Interpretative Phenomenological Analysis (IPA); this seeks to describe and provide understanding of people’s experience of a phenomenon by studying in-depth a small number from a relatively homogeneous group (women with SLE in the present study). Analysis revealed three themes concerning appearance issues. Participants described public self-consciousness after the onset of SLE. Cosmetics and clothing were used skilfully to appear ‘normal’, hide the ‘self’ and assert control but could increase feelings of difference and isolation. Self-imposed isolation was also described and may relate to depression. The understanding of family, friends, colleagues and healthcare providers was also important. Awareness of the psychosocial concerns of SLE patients with life-changing skin disease may enable multidisciplinary healthcare teams to offer a more sensitive, practical service. The physical and emotional needs of SLE patients need to be ascertained and appropriate educational and psychological services are required.

Selected Aspects in the Pathogenesis of Autoimmune Diseases

Autoimmune processes can be found in physiological circumstances. However, they are quenched with properly functioning regulatory mechanisms and do not evolve into full-blown autoimmune diseases. Once developed, autoimmune diseases are characterized by signature clinical features, accompanied by sustained cellular and/or humoral immunological abnormalities. Genetic, environmental, and hormonal defects, as well as a quantitative and qualitative impairment of immunoregulatory functions, have been shown in parallel to the relative dominance of proinflammatory Th17 cells in many of these diseases. In this review we focus on the derailed balance between regulatory and Th17 cells in the pathogenesis of autoimmune diseases. Additionally, we depict a cytokine imbalance, which gives rise to a biased T-cell homeostasis. The assessment of Th17/Treg-cell ratio and the simultaneous quantitation of cytokines, may give a useful diagnostic tool in autoimmune diseases. We also depict the multifaceted role of dendritic cells, serving as antigen presenting cells, contributing to the development of the pathognomonic cytokine signature and promote cellular and humoral autoimmune responses. Finally we describe the function and role of extracellular vesicles in particular autoimmune diseases. Targeting these key players of disease progression in patients with autoimmune diseases by immunomodulating therapy may be beneficial in future therapeutic strategies.

Assessment of intracellular cytokines and regulatory cells in patients with autoimmune diseases and primary immunodeficiencies - novel tool for diagnostics and patient follow-up

Serum and intracytoplasmic cytokines are mandatory in host defense against microbes, but also play a pivotal role in the pathogenesis of autoimmune diseases by initiating and perpetuating various cellular and humoral autoimmune processes. The intricate interplay and fine balance of pro- and anti-inflammatory processes drive, whether inflammation and eventually organ damage will occur, or the inflammatory cascade quenches. In the early and late, as well as inactive and active stages of autoimmune diseases, different cellular and molecular patterns can dominate in these patients. However, the simultaneous assessment of pro- and anti-inflammatory biomarkers aids to define the immunological state of a patient. A group of the most useful inflammatory biomarkers are cytokines, and with increasing knowledge during the last decade their role have been well-defined in patients with autoimmune diseases and immunodeficiencies. Multiple pathological processes drive the development of autoimmunity and immunodeficiencies, most of which involve quantitative and qualitative disturbances in regulatory cells, cytokine synthesis and signaling pathways. The assessment of these biomarkers does not aid only in the mechanistic description of autoimmune diseases and immunodeficiencies, but further helps to subcategorize diseases and to evaluate therapy responses. Here, we provide an overview, how monitoring of cytokines and regulatory cells aid in the diagnosis and follow-up of patients with autoimmune diseases and immunodeficiencies furthermore, we pinpoint novel cellular and molecular diagnostic possibilities in these diseases.

Systemic sclerosis: demographic, clinical and serological features in 100 Iranian patients

To evaluate demographic, clinical and laboratory features associated with scleroderma-specific auto-antibodies. Sera of 100 patients with systemic sclerosis (SSc) were analyzed by an indirect immunofluorescence technique with HEp-2 cells as a substrate. Specific ANA such as anti-centromere antibodies (ACA), anti-topoisomerase (TOPO), anti-RNA polymerase III (Pol 3), anti-U3-RNP (U3-RNP), anti-Th/To (Th/To) and anti-PM/Scl (PM/Scl) were detected by line immunoassay and anti-U1-RNP (U1-RNP) by ELISA. Frequency of clinical features associated with a specific antibody group was reported cumulatively over the follow-up period. Frequency of specific clinical features was compared across the two disease subtype including limited cutaneous (lcSSc) or diffuse cutaneous (dcSSc) as well as the auto-antibody groups. Ninety-four percent of patients were ANA positive with significant higher skin score, Raynauds and digital ulcer/gangrene. Anti-TOPO was detected in 71% of all patients, in 90.5% of dcSSC and in 65.8% of lcSSc. Anti-TOPO was significantly associated with dcSSc, higher skin score, digital ulcer/gangrene, pulmonary fibrosis, DLCO <70%. U1-RNP antibody was associated with lower fibrosis in lung. ACA was positive in 7% of patients and exclusively in those with lcSSc. We did not find association between gender and presence of auto-antibodies. Anti-TOPO antibody had a high prevalence in contrast to low prevalence of ACA antibody. There were no differences in clinical subtypes of the disease in patients with positive anti-TOPO and positive ACA. Differences in prevalence of auto-antibodies are suggestive of further genetic study.

Environment and lupus-related diseases

Clinical manifestations of lupus are encountered in a variety of disease entities, including isolated cutaneous lupus, undifferentiated connective tissue disease, mixed connective tissue disease, drug-induced lupus, overlap syndrome, and systemic lupus erythematosus (SLE). While each entity has been recognized as a specific disease with its own diverse clinical and serological pattern, one could argue that many findings are common. Could it be that all of these entities actually represent a spectrum of one disease? Could it be that rather than the genetic predisposition and hence controlled factors that govern this spectrum of diseases, that environmental factors associated with SLE could also play a role in the different entities of this spectrum? The traditional environmental triggers in SLE include sunlight and ultraviolet (UV) light, infections, smoking, and medications including biologics such as tumor necrosis factor alpha (TNF-a) blockers. In this review, we update and further substantiate these traditional factors in the various lupus-related syndromes. We will also discuss the association with vaccine exposure, industrial estrogens, and other factors.

Gender and ethnicity differences in the prevalence of scleroderma-related autoantibodies

Autoantibodies to topoisomerase I (topo I), RNA polymerase III (RNAPIII), centromere, U3RNP/fibrillarin, Th, PM-Scl, and U1RNP found in scleroderma (SSc) are associated with unique clinical subsets. The effects of race and gender on autoantibody prevalence and clinical manifestations were examined. Autoantibodies in sera from 105 SSc (include 75 Caucasian, 24 African-American, 6 others; 89 females and 16 males) were analyzed by immunofluorescence and immunoprecipitation. Clinical information was from database. SSc-related autoantibodies seldom coexist except for anti-topo I and anti-U1RNP. Anti-topo I (35% vs 15%), anti-U3RNP (30% vs 3%, p = 0.0005), and anti-U1RNP (30% vs 13%) were more common in African-Americans vs Caucasians. Anti-centromere (17%) and anti-PM-Scl (only in 8% of female) were found only in Caucasians. In race/gender combination, all three African-American males had anti-topo I (p = 0.04). Anti-U3RNP (35% vs 3%, p = 0.0005) and anti-U1RNP were common in African-American females. In African-American, all nucleolar dominant staining sera had anti-U3RNP; nuclear pattern was topo I (50%), U1RNP (19%), and RNAPIII (13%). In Caucasian, nucleolar was anti-Th (43%) and PM-Scl (29%); nuclear pattern was RNAPIII (29%), topo I (24%), and U1RNP (18%). Anti-topo I, anti-RNAPIII, and anti-U3RNP were associated with diffuse SSc while anti-centromere, anti-Th, and anti-U1 with limited disease. Proximal scleroderma was less common in African-American with anti-topo I (38% vs 91% in Caucasian, p = 0.04). The production of SSc-related autoantibodies is gender and race dependent, and this can be highly relevant in understanding their clinical significance.

Lateral cantholysis for cataract surgery

A patient with narrow palpebral aperture who required an elaborate lateral cantholysis prior to uncomplicated phacoemulsification surgery is described. Surgery was followed by a lateral tarsal strip procedure to reattach the lower lid.

Coexistence of five autoimmune diseases: diagnostic and therapeutic difficulties

We report the case of coexistence of five autoimmune diseases in a 36-year-old woman, who initially developed psoriasis. Several years later, the patient was diagnosed with a mixed connective tissue disease and primary biliary cirrhosis (PBC). On admission to the Department of Rheumatology and Connective Tissue Diseases, the patient fulfilled classification criteria of an overlap syndrome systemic lupus erythematosus (SLE) with secondary antiphospholipid syndrome/systemic sclerosis (SSc)/Sjogren's syndrome (SS) with coexisting PBC and psoriasis. The SLE symptoms included discoid lupus erythematosus, arthritis, pancytopenia, antinuclear antibodies and anticardiolipin antibodies. Moreover, the patient met the criteria of antiphospholipid syndrome diagnosed based on preterm delivery before week 34, and high values of anticardiolipin antibodies were found at repeated determinations. The SSc symptoms included sclerodactyly, pulmonary fibrosis with pulmonary hypertension and esophageal dysfunction. The SS syndrome involved xerostomia, xerophthalmia, the positive Schirmer's test and presence of anti-SS antibodies. The literature reports overlap syndromes in various combinations; however, the coexistence of five autoimmune diseases is extremely rare.

The development of connective tissue diseases in patients with autoimmune hepatitis: a case series

OBJECTIVES

To study the prevalence of connective tissue diseases (CTD) in patients with autoimmune hepatitis (AIH).

METHODS

We identified 11 cases of AIH over the past 7 years at our institution, through a systematic chart review of patients with this diagnosis. Their charts were reviewed for the development of systemic CTD.

RESULTS

Three of the 11 patients with a definitive diagnosis of AIH developed systemic CTD. All were white: 2 women and 1 man, with an age range of 33 to 62 years, and with disease duration of 1 to 7 years. One patient developed systemic lupus erythematosus (SLE) with vasculitis and peripheral neuropathy. The second developed limited scleroderma and the third developed undifferentiated connective tissue disease (UCTD) and interstitial lung disease. There appear to be shared susceptibility alleles for AIH and CTD in addition to the shared positive autoantibodies.

CONCLUSIONS

Patients with AIH may be at increased risk for developing systemic CTD. Conversely, a review of the literature reveals that patients with systemic CTD may be at increased risk of developing AIH. Patients with either AIH or CTD should be monitored for further development of concurrent autoimmune diseases.

A case of overlap syndrome with rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis and secondary Sjögren's syndrome

We report an unusual case of overlap syndrome that had the coexistence of five autoimmune diseases. A 45-year-old woman initially developed seropositive erosive rheumatoid arthritis (RA) 11 years ago. She then developed progressive systemic sclerosis (PSS) (including pulmonary hypertension, esophageal dysfunction, cardiac involvement and sclerodactilitis), systemic lupus erythematosus (SLE) (including photosensitivity, nephritis, leukopenia, lymphopenia, thrombocytopenia and Coombs positive hemolytic anemia and positive anti-dsDNA), and secondary Sjögren's syndrome (SSS) in the last 7 years before she was admitted to our clinic. The patient fulfilled classification criteria for RA, SLE, PSS and SSS, as determined by American College of Rheumatology. Hypothyroidism with positive autoantibodies due to Hashimoto's thyroiditis, the beginning of which could not be defined, was coexistent with this overlap syndrome. In the literature, although overlap syndromes in different combinations were reported, we very rarely observed a complex case like this patient. In our opinion, this is the first well-documented case of RA, PSS, SLE, SSS and Hashimoto's thyroiditis existing together in the same patient. Although immunosuppressive therapy was administered, the disease rapidly deteriorated and the patient died.

The prognosis of mixed connective tissue disease

The prognosis for patients who have mixed connective tissue disease (MCTD) varies from a benign course to severe progressive disease. In approximately one third of patients the clinical symptoms go into long-term remission and the anti-U1 small nuclear ribonucleoprotein antibodies disappear. One third of patients have a severe, progressive disease course. Persistent morbidity often is attributable to arthritis, easy fatiguability, and dyspnea on exertion. The most severe clinical manifestation is pulmonary hypertension which contributes to premature death in patients who have MCTD. Pulmonary hypertension is associated with proliferative vascular abnormalities that involve small pulmonary vessels, rather than interstitial lung disease.

Autoantibodies in systemic sclerosis

OBJECTIVES

To describe the clinical, laboratory, and prognostic features associated with the scleroderma-specific autoantibodies.

METHODS

Using the Pittsburgh Scleroderma Databank, all consecutive patients seen between 1980 and 1995 who had autoantibody studies performed were studied. Anticentromere antibodies (ACA), antitopoisomerase (TOPO), anti-U1-RNP (U1-RNP), anti-RNA Polymerase III (Pol 3), anti-U3-RNP (U3-RNP), anti-Th/To (Th/To), and anti-Pm/Scl (Pm/Scl) were determined according to previously described methods. The frequency of clinical features, organ system outcomes, and survival within the patients with a specific antibody were cumulative over the course of the disease. The frequency of a specific feature was compared across groups to identify significant manifestations and outcomes in patients with a specific antibody.

RESULTS

Some demographic, clinical, and organ system findings were associated with the specific antibody, and other features with the scleroderma subtype (limited cutaneous or diffuse cutaneous scleroderma). U3-RNP, U1-RNP, and TOPO were seen more commonly in African-American patients, and ACA was seen in older, female Caucasians. Muscle inflammation was seen in patients with U1-RNP and U3-RNP. Digital tip ulcers and digital tuft resorption were seen more frequently in those with ACA and TOPO. A vasculopathy causing pulmonary hypertension typically occurs with ACA and pulmonary fibrosis with TOPO; however, both types of lung disease were seen in patients with nucleolar antibodies, Th/To and U3-RNP. Importantly, severe interstitial fibrosis was rarely seen in cases with Pol 3. Renal crisis was strongly associated with Pol 3. Survival within limited scleroderma was decreased in the Th/To patients compared with ACA patients. Within the diffuse scleroderma group, patients with Pol 3 had the best survival.

CONCLUSIONS

Scleroderma autoantibodies are associated with very specific demographic, clinical, organ system, and survival features.

RELEVANCE

The determination of scleroderma autoantibodies may be helpful in assessing the prognosis, monitoring, and treatment of scleroderma patients.

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.

Dendritic cells under investigation in autoimmune disease

Autoimmune disorders play an increasing role in public health, especially in light of the fact of the growing aged population, which primarily develop such diseases. A clear understanding of the mechanisms leading to the development of autoimmune responses and finally to autoimmune disease does not exist. Autoimmunity is characterized by the presence of autoantibodies and/or autoreactive T cells and the corresponding organ manifestation. Following the discovery of autoreactive T cells found in the periphery of mice and humans, the old immunological concept that autoreactive T cells are completely deleted in the thymus during evolution has been revised in recent years. Although antigen-presenting cells and particularly dendritic cells are known to play an important role in the regulation of immune responses and the activation of T cells, recent evidence suggests that the role of dendritic cells in the development of autoimmunity has been underestimated previously. This article aims to give a general overview on the basic immunological principles involved and gives a short review of the current literature on the functional relevance of dendritic cells in various human and murine autoimmune disorders.

Efficacy of pulsed intravenous immunoglobulin therapy in mixed connective tissue disease

We describe a 69-year-old patient with long-standing mixed connective tissue disease who suffered from severe skin eruptions that did not respond to various immunosuppressive regimens. Therapy with high-dose intravenous immunoglobulin was successful in controlling the patient's disease without major side effects. We think that this regimen-although expensive-might be an interesting therapeutic option in selected patients with mixed connective tissue disease that is refractory to other treatment modalities.

Overexpression of CD40 ligand in murine epidermis results in chronic skin inflammation and systemic autoimmunity

CD40-CD40 ligand (L) interactions play a pivotal role in immune-mediated inflammatory responses via the activation of antigen-presenting cells (APCs). To investigate the effects of continuous activation of resident tissue APCs, in this case the Langerhans cells (LCs) of the skin, CD40L expression was targeted to the basal keratinocytes of the epidermis of mice using the keratin-14 promoter. Approximately 80% of the transgenic (Tg) mice spontaneously developed dermatitis on the ears, face, tail, and/or paws. Compared with littermates, Tgs had a >90% decrease in epidermal LCs yet increased numbers within the dermis suggestive of enhanced emigration of CD40-activated LCs. Tgs also displayed massive regional lymphadenopathy with increased numbers of dendritic cells and B cells. Moreover, a decrease in IgM and an increase in IgG1/IgG2a/IgG2b/IgE serum concentrations was detectable. Screening for autoantibodies revealed the presence of antinuclear antibodies and anti-dsDNA antibodies implicative of systemic autoimmunity. Accordingly, renal Ig deposits, proteinuria, and lung fibrosis were observed. Adoptive transfer of T cells from Tgs to nonTg recipients evoked the development of skin lesions similar to those found in the Tgs. Dermatitis also developed in B cell-deficient CD40L Tg mice. These findings suggest that in situ activation of LCs by CD40L in the skin not only leads to chronic inflammatory dermatitis but also to systemic mixed-connective-tissue-like autoimmune disorders, possibly by breaking immune tolerance against the skin.

Autoantibodies and overlap syndromes in autoimmune rheumatic disease

Many patients diagnosed with autoimmune rheumatic disease cannot be categorised easily into one of the established clinical entities such as systemic lupus erythematosus, dermatomyositis, or systemic sclerosis. The term "overlap syndrome" has been increasingly used to identify such patients and is useful in terms of clarifying prognosis and facilitating disease management. This article reviews overlap syndrome in autoimmune rheumatic disease, with particular emphasis on the associated serological markers.