[Mixed connective tissue disease and its management]. / La connectivite mixte et sa prise en charge.

Mixed connective tissue disease (MCTD) is a rare autoimmune condition. Since its first description 50 years ago, its mere existence has been debated, given that it shares features of other autoimmune diseases, such as systemic lupus erythematosus (SLE), systemic sclerosis, inflammatory myopathy, rheumatoid arthritis and Sjogren's syndrome. Also, while antibodies to U1-RNP are essential for the diagnosis of MCTD, these antibodies may be expressed in other circumstances, such as in case of SLE. Nevertheless, the patient fulfilling criteria for MCTD needs specific management. In this review, we describe the clinical features and the potential complications of this complex disease, often wrongly disregarded as benign. We will also emphasize the recommended follow-up exams and address treatment, which is currently lacking formal recommendations.

La connectivite mixte (mixed connective tissue disease (MCTD)) est une maladie auto-immune rare. Dès sa description il y a cinquante ans, l'existence propre de la MCTD est débattue, car les limites avec d'autres maladies, comme le lupus érythémateux systémique (LES), la sclérodermie, les myopathies inflammatoires, la polyarthrite rhumatoïde et le syndrome de Sjögren, sont floues. Les anticorps anti-U1-RNP obligatoires au diagnostic de MCTD sont également exprimés dans d'autres circonstances, comme le LES. Quoi qu'il en soit, le patient présentant des critères de MCTD nécessite une prise en charge spécifique. Nous présentons ici les signes cliniques et complications potentielles d'une maladie longtemps estimée à tort comme d'évolution bénigne. Nous abordons aussi les examens de suivi recommandés et la thérapeutique, qui reste à ce jour mal définie.

Childhood mixed connective tissue disease at disease onset: Evidence from a systematic review.

OBJECTIVE: Childhood Mixed Connective Tissue Disease (cMCTD) is the rarest pediatric connective tissue disease that includes features of systemic lupus erythematosus, polymyositis/dermatomyositis, juvenile idiopathic arthritis, and systemic sclerosis, identified by Sharp in 1972 and whose diagnosis remains challenging. This systematic review aims to identify clinical features at the onset of cMCTD and manifestations not currently included into the available diagnostic criteria. METHODS: A systematic literature review was performed in accordance with PRISMA guidelines 2020 using bibliographic databases: MEDLINE via PubMed and EMBASE. ELIGIBILITY CRITERIA: patients diagnosed with MCTD with onset before 18 years. STUDIES INCLUDED: registries, retrospective and prospective cohort studies, case series and reports with analysis of data on signs and symptoms of presentation. RESULTS: 39 articles were included (215 subjects, 82.5% female), mean age of 141 months (± 41 months DS, range 2.5-204). The most used criteria for the diagnosis of MCTD were the Kasukawa criteria (54.5%). The clinical manifestations described at onset were Raynaud's phenomenon (69.7%), arthritis (60.9%), muscular involvement (53.5%), dermatological signs (39.5%), swollen fingers or hands (29.3%), arthralgias (25.6%), fever (22.3%), lung involvement (14.4%), sclerodactily (13.5%), lymphadenopathy (10.7%) serositis (10.2%), esophageal involvement (6.9%), nervous system involvement (6.9%), xeroftalmia (3.7%), xerostomia (3.7%), hepatosplenomegaly (2.8%), cardiac involvement (2.8%), hepatitis (2.3%), parotiditis (2.3%), Hashimoto's thyroiditis (0.9%), ocular involvement (0.9%). CONCLUSIONS: The data from this systematic review suggest great heterogeneity of the clinical presentation of cMCTD for which there are no validated diagnostic criteria that may suggest a new diagnostic approach to allow earlier or more accurate diagnosis in the future.

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.

Mixed connective tissue disease-myositis overlap syndrome presenting as an allergic disease process to the emergency department: A case report.

BACKGROUND: The "allergy epidemic" of the Western World, has led to an overwhelming number of emergency department presentations with allergic rhinitis, allergic conjunctivitis, atopic eczema, and asthma. Careful consideration should be given to screening for the typical signs and symptoms of Mixed connective tissue disease (MCTD) in patients presenting to the ED with what appears to be a simple allergic process. MCTD is a rare systemic rheumatic disease characterized by high levels of anti-U1RNP antibodies and various clinical signs and symptoms. The pathophysiology of MCTD is poorly understood. An association between allergen-mediated processes and MCTD has been reported in recent literature. Our case report involves a 40 year old African American female with initial outpatient presentation suggestive of atopic disease, with progressive worsening of symptoms while receiving allergen immunotherapy. The patient presented to the emergency department with bilateral leg cramping. The patient was found to have a CPK of 7000 unresponsive to fluids. The patient was evaluated by the Allergy and Rheumatology services. The patient was ultimately diagnosed with MCTD-Myositis Overlap Syndrome and started on steroids and IVIG with improvement in symptoms. While MCTD is not a diagnosis readily made in the ED, early identification and treatment of the disease is critical for prevention of long term complications.

Mixed Connective Tissue Disease as Different Entity: Global Methylation Aspect.

Mixed connective tissue disease (MCTD) is a very rare disorder that belongs in the rare and clinically multifactorial groups of diseases. The pathogenesis of MCTD is still unclear. The best understood epigenetic alteration is DNA methylation whose role is to regulate gene expression. In the literature, there are ever-increasing assumptions that DNA methylation can be one of the possible reasons for the development of Autoimmune Connective Tissue Diseases (ACTDs) such as systemic sclerosis (SSc) and systemic lupus erythematosus (SLE). The aim of this study was to define the global DNA methylation changes between MCTD and other ACTDs patients in whole blood samples. The study included 54 MCTD patients, 43 SSc patients, 45 SLE patients, and 43 healthy donors (HC). The global DNA methylation level was measured by ELISA. Although the global DNA methylation was not significantly different between MCTD and control, we observed that hypomethylation distinguishes the MCTD patients from the SSc and SLE patients. The present analysis revealed a statistically significant difference of global methylation between SLE and MCTD (p < 0.001), SLE and HC (p = 0.008), SSc and MCTD (p ≤ 0.001), and SSc and HC (p < 0.001), but neither between MCTD and HC (p = 0.09) nor SSc and SLE (p = 0.08). The highest % of global methylation (median, IQR) has been observed in the group of patients with SLE [0.73 (0.43, 1.22] and SSc [0,91 (0.59, 1.50)], whereas in the MCTD [0.29 (0.20, 0.54)], patients and healthy subjects [0.51 (0.24, 0.70)] were comparable. In addition, our study provided evidence of different levels of global DNA methylation between the SSc subtypes (p = 0.01). Our study showed that patients with limited SSc had a significantly higher global methylation level when compared to diffuse SSc. Our data has shown that the level of global DNA methylation may not be a good diagnostic marker to distinguish MCTD from other ACTDs. Our research provides the groundwork for a more detailed examination of the significance of global DNA methylation as a distinguishing factor in patients with MCTD compared to other ACTDs patients.

Anti-SMN autoantibodies in mixed connective tissue disease are associated with a severe systemic sclerosis phenotype.

OBJECTIVES: The survival of motor neuron (SMN) complex has an essential role in the assembly of small nuclear ribonucleoproteins (RNP). Recent reports have described autoantibodies (aAbs) to the SMN complex as novel biomarkers in anti-U1RNP+ myositis patients. The aim of this study was to compare phenotypic features of anti-U1RNP+ mixed connective tissue disease (MCTD) patients with and without anti-SMN aAbs. METHODS: A retrospective MCTD cohort was studied. Addressable laser bead immunoassay was used to detect specific anti-SMN aAbs with <300 mean fluorescence intensity (MFI) as normal reference range, 300-999 MFI as low-titre and ≥1000 MFI as high-titre positivity. Comparison of clinical features between anti-SMN+ and anti-SMN- subgroups used two-tailed Fisher's exact test, and logistic regression analyses. RESULTS: Sixty-six patients were included. Median age at MCTD diagnosis was 40.6 years, and duration of follow-up was 12 years. Based on the highest available titre, 39 (59%) were anti-SMN+: 10 (26%) had low titre and 29 (74%) had high titre. Anti-SMN+ patients had a higher frequency of fingertip pitting scars (anti-SMN+ 23% vs anti-SMN- 4%, p=0.04), lower gastrointestinal (GI) involvement (26% vs 4%, p=0.04), and myocarditis (16% vs 0%, p=0.04). The combined outcome of pitting scars and/or lower GI involvement and/or myositis and/or myocarditis was highest among high-titre anti-SMN+ patients: adjusted OR 7.79 (2.33 to 30.45, p=0.002). CONCLUSIONS: Anti-SMN aAbs were present in 59% of our MCTD cohort. Their presence, especially at high-titres, was associated with a severe systemic sclerosis (scleroderma) phenotype including myositis, myocarditis and lower GI involvement.

An unusual cardiac involvement in mixed connective tissue disease / Una afección cardíaca poco común en la enfermedad mixta del tejido conjuntivo

Mixed connective tissue disease is an autoimmune disorder with overlapping features of systemic lupus erythematosus, systemic sclerosis and polymyositis. Cardiac involvement is common, being pericarditis the most frequent manifestation, as also pulmonary hypertension. The authors present a case of a woman with one year of symptoms of polyarthritis and myalgia with gradual muscle weakness and weight loss, with severe impaired mobility in the last months. The initial evaluation showed an inflammatory systemic condition with an infiltrative pattern in echocardiogram, with pulmonary hypertension, that was confirmed by cardiac magnetic resonance. After an extensive study, where infiltrative cardiomyopathies were a differential diagnosis, the patient meet criteria to mixed connective disease with signs of pulmonary hypertension and an atypical cardiac involvement. Immunosuppressive treatment and rehabilitation were initiated and one year after the patient remains asymptomatic without any limitations. (AU)

La enfermedad mixta del tejido conectivo es un trastorno autoinmune con características superpuestas de lupus eritematoso sistémico, esclerosis sistémica y polimiositis. La afectación cardiaca es común, siendo la pericarditis la manifestación más frecuente, al igual que la hipertensión pulmonar. Los autores presentan el caso de una mujer con un año de síntomas de poliartritis y mialgia con debilidad muscular gradual y pérdida de peso, con grave deterioro de la movilidad en los últimos meses. La evaluación inicial mostró un cuadro inflamatorio sistémico con patrón infiltrativo en ecocardiograma, con hipertensión pulmonar, que se confirmó por resonancia magnética cardiaca. Tras un amplio estudio, en el que las miocardiopatías infiltrativas constituyeron un diagnóstico diferencial, la paciente cumplía criterios de conectivopatía mixta con signos de hipertensión pulmonar y una afectación cardiaca atípica. Se inició tratamiento inmunosupresor y rehabilitación y un año después la paciente permanece asintomática sin limitaciones. (AU)

FROSTED BRANCH ANGIITIS ASSOCIATED WITH MIXED CONNECTIVE TISSUE DISEASE.

PURPOSE: To present a case of frosted branch angiitis associated with an exacerbation of mixed connective tissue disease (MCTD). METHODS: Single case report. RESULTS: A 31-year-old woman presented with a flare of her long-standing MCTD after a change in her immunosuppressive medications. She developed blurred vision and floaters first in the left eye but eventually in both eyes. Fundoscopy showed patchy perivascular sheathing of tertiary branch venules surrounded by retinal hemorrhages characterized as frosted branch angiitis. The patient's MCTD symptoms and retinal vasculitis improved with continued immunosuppressive therapy. At 1-month follow-up, her visual acuity had improved to 20/20 bilaterally with complete resolution on fundoscopy. CONCLUSION: To the authors' knowledge, this is the first report of frosted branch angiitis seen in association with MCTD. The improvement in the patient's visual acuity and fundoscopic findings in this case supports the role of immunosuppressive therapy to treat secondary frosted branch angiitis associated with an autoimmune condition such as MCTD. However, it is recommended that a comprehensive medical workup is performed to exclude an infective cause, particularly in immunocompromised patients.

Doubtful Clinical Value of Subtyping Anti-U1-RNP Antibodies Regarding the RNP-70 kDa Antigen in Sera of Patients with Systemic Lupus Erythematosus.

The detection of antinuclear antibodies is central to the diagnosis and prognosis of systemic lupus erythematosus (SLE), primary Sjögren's syndrome (pSS) and mixed connective tissue disease (MCTD). Anti-U1-RNP and anti-RNP70 antibodies were assayed in the sera of patients with SLE (n = 114), pSS (n = 54) and MCTD (n = 12). In the SLE group, 34/114 (30%) were anti-U1-RNP positive, and 21/114 (18%) were both anti-RNP70 positive and anti-U1-RNP positive. In the MCTD group, 10/12 (83%) were anti-U1-RNP positive, and 9/12 (75%) were anti-RNP70 positive. Only one individual with pSS was antibody positive (for both anti-U1-RNP and anti-RNP70). All anti-RNP70-positive samples were also anti-U1-RNP positive. Anti-U1-RNP-positive subjects with SLE were younger (p < 0.0001); showed lower concentrations of complement protein 3 (p = 0.03); had lower eosinophil (p = 0.0005), lymphocyte (p = 0.006) and monocyte (p = 0.03) counts; and had accrued less organ damage (p = 0.006) than the anti-U1-RNP-negative SLE patients. However, we observed no significant clinical or laboratory parameter differences between the anti-U1-RNP-positive individuals with/without anti-RNP70 in the SLE group. In conclusion, anti-RNP70 antibodies are not exclusive to MCTD but are rarely detected in pSS and healthy individuals. In SLE, anti-U1-RNP antibodies are associated with a clinical phenotype that resembles MCTD, with hematologic involvement and less damage accrual. Based on our results, the clinical value of subtyping anti-RNP70 in anti-U1-RNP-positive sera appears to be of limited value.

An Unusual Case of Telangiectasias.

BACKGROUND: Telengiectasias are defined as persistent dilatation of small capillaries in the superficial dermis Case : A 26-year-old woman presented with red lesions, epistaxis, joint pains, color changes of the hands, and breathlessness. On clinical examination and investigations, a final diagnosis of mixed connective tissue disease (MCTD), with interstitial lung disease (ILD), with telangiectasias, and epistaxis was made. Telangiectasias and epistaxis are rare presentations of MCTD.

Population-based prevalence and incidence estimates of mixed connective tissue disease from the Manhattan Lupus Surveillance Program.

OBJECTIVE: Epidemiological data for MCTD are limited. Leveraging data from the Manhattan Lupus Surveillance Program (MLSP), a racially/ethnically diverse population-based registry of cases with SLE and related diseases including MCTD, we provide estimates of the prevalence and incidence of MCTD. METHODS: MLSP cases were identified from rheumatologists, hospitals and population databases using a variety of International Classification of Diseases, Ninth Revision codes. MCTD was defined as one of the following: fulfilment of our modified Alarcon-Segovia and Kahn criteria, which required a positive RNP antibody and the presence of synovitis, myositis and RP; a diagnosis of MCTD and no other diagnosis of another CTD; and a diagnosis of MCTD regardless of another CTD diagnosis. RESULTS: Overall, 258 (7.7%) cases met a definition of MCTD. Using our modified Alarcon-Segovia and Kahn criteria for MCTD, the age-adjusted prevalence was 1.28 (95% CI 0.72, 2.09) per 100 000. Using our definition of a diagnosis of MCTD and no other diagnosis of another CTD yielded an age-adjusted prevalence and incidence of MCTD of 2.98 (95% CI 2.10, 4.11) per 100 000 and 0.39 (95% CI 0.22, 0.64) per 100 000, respectively. The age-adjusted prevalence and incidence were highest using a diagnosis of MCTD regardless of other CTD diagnoses and were 16.22 (95% CI 14.00, 18.43) per 100 000 and 1.90 (95% CI 1.49, 2.39) per 100 000, respectively. CONCLUSIONS: The MLSP provided estimates for the prevalence and incidence of MCTD in a diverse population. The variation in estimates using different case definitions is reflective of the challenge of defining MCTD in epidemiologic studies.

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.

[Standardized diagnosis and treatment of undifferentiated connective tissue disease and mixed connective tissue disease].

Undifferentiated connective tissue disease (CTD) usually refers to patients who are presented with certain symptoms and signs related to CTD, and positive serological evidence of autoimmune diseases but don't fulfill any of the classification criteria for a certain CTD. Mixed CTD refers to patients who are presented with one or more clinical manifestations such as hand swelling, synovitis, myositis, Raynaud's phenomenon, and acrosclerosis. Patients with mixed CTD always have high-titer anti-nuclear antibodies (ANA) of speckled pattern and high-titer anti-U1 ribonuclear protein (RNP) antibody in serum, while with negative anti-Sm antibody. The update of diagnosis and treatment of undifferentiated CTD and mixed CTD lags behind other established CTD. There is a lack of evidence from randomized controlled trials or guidelines/recommendations on the treatment of undifferentiated CTD or mixed CTD. At present, the conventional therapy is mainly adopted according to the specific clinical manifestations of the disease. The standardized diagnosis and treatment of undifferentiated CTD and mixed CTD were drafted by the Chinese Rheumatology Association based on the previous guidelines and the progress of available evidence, so as to improve the management of these patients in China.

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.

Capillaroscopic analysis of the microvascular status in mixed versus undifferentiated connective tissue disease.

INTRODUCTION: Raynaud phenomenon (RP), typically, precede the clinical onset of systemic manifestations in several connective tissue diseases (CTDs). These autoimmune disorders usually share a microvascular damage whose alterations can be detected by nailfold videocapillaroscopy (NVC). The aim of the study was to compare the NVC microvascular status in Mixed Connective Tissue Disease (MCTD) versus the Undifferentiated Connective Tissue Disease (UCTD), and to search correlations between NVC findings and specific autoantibodies in UCTD patients. METHODS: Clinical data and NCV patterns were retrospectively obtained from the files of 46 MCTD patients, 47 stable UCTD patients and 51 individuals with primary RP (PRP) as controls collected in a central database (VideoCap®, DS Medica, Milan, Italy). ANA and ENA Abs were tested respectively by indirect immunofluorescence and enzyme-linked immunosorbent assay. RESULTS: "Scleroderma-like" (SSc-like) NVC pattern was significantly more frequent in MCTD than in UCTD patients (48% vs 11%, p < 0.001). Giant capillaries, abnormal shapes (i.e. neoangiogenesis) and lower capillary density were predominantly detected among MCTD versus UCTD patients (48% vs 11%, 49% vs 13%, 52% vs 9%, respectively, p < 0.001). The absolute number of capillaries was significantly lower in MCTD versus UCTD patients (mean 7 ± 1.7 SD vs mean 9.2 ± 1.3 SD, respectively, p < 0.001). Fully normal NVC pattern and non-specific NVC alterations were respectively observed in 6% and 46% of MCTD and in 6% and 83% of UCTD. Moreover, PRP patients showed normal NVC pattern and non-specific capillary abnormalities in 23% and in 77%, respectively. No statistically significant correlations were observed between NVC patterns and ANA patterns/specific ENA-Abs among the UCTD patients. CONCLUSIONS: The significant presence of the SSc-like NVC pattern and reduced number of capillaries seem the most typical NVC findings in MCTD in comparison to UCTD patients, suggesting a reflection of more complex and severe disease in MCTD ones.

Nailfold capillaroscopy changes associated with anti-RNP antibodies in systemic lupus erythematosus.

Anti-U1RNP antibody is associated with distinct organ involvement in patients with systemic lupus erythematosus (SLE). Nailfold capillaroscopy (NFC) allows non-invasive assessment of microvascular abnormalities in several connective tissue diseases. The objective of this study is to determine the association of anti-U1RNP antibody with microvascular changes by NFC in RNP-positive SLE patients in comparison with RNP-negative SLE patients (negative disease controls) and mixed connective tissue disease (MCTD) cases (positive disease controls). NFC examination was performed in consecutive patients with SLE with or without anti-U1RNP positivity. MCTD patients were recruited as disease controls. Abnormalities noted in the three groups were compared using non-parametric tests. Ordinal logistic or linear regression was used wherever applicable. 81 patients were studied, of whom 28 were diagnosed as RNP-positive SLE (age 30.0 ± 10.37; 26 females), 26 were RNP-negative SLE (age 29.42 ± 9.20; 25 females) and 27 had MCTD (age36.5 ± 9.70; 25 females). RNP-positive SLE patients had more frequent giant capillaries, enlarged capillaries and ramified capillaries as compared to RNP-negative SLE (p = 0.05, < 0.01 and 0.03, respectively). The capillary density was lower in patients with MCTD as compared with patients with RNP-positive SLE (5.11 ± 1.69/mm vs 7.25 ± 1.38/ mm, p < 0.01) and RNP-negative SLE (8.92 ± 1.13/mm, p < 0.01). The reduction in capillary density was less severe in patients with RNP-negative SLE as compared with RNP-positive SLE (OR = 0.1058 [95% CI = 0.02-0.546], p < 0.01) which was independent of the presence of Raynaud's phenomenon, interstitial lung disease and disease duration. Presence of anti-U1RNP antibody is associated with notable patterns of microvascular abnormalities in SLE. These NFC abnormalities are noted more profoundly in patients with MCTD and are less marked in RNP-negative SLE patients.