Magnetic Resonance Imaging Patterns Revealing Muscle Pathology and Clinical Features in Idiopathic Inflammatory Myopathies.

OBJECTIVE: Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders significantly impacting skeletal muscles; however, the precise correlation between muscle magnetic resonance imaging (MRI) findings, muscle pathology, disease subtypes, and clinical characteristics remains uncertain. Thus, we investigated the association of muscle MRI findings in IIMs with muscle pathology and clinical features. METHODS: New-onset IIM patients underwent proximal upper and/or lower limb muscle MRI. Patterns of muscle oedema on MRI were categorised into fascial, honeycomb, peripheral, foggy, dense, or coarse dot patterns and compared with inflammatory cell infiltration sites in corresponding muscle biopsies. The incidence of MRI patterns was examined in patient subgroups using myositis-specific antibodies (MSAs) and 2017 EULAR/ACR classification criteria. Univariate and multivariate analyses were conducted to determine the odds ratios (ORs) of MRI findings for clinical characteristics. RESULTS: Fifty-six of 85 patients underwent muscle biopsy. Foggy, honeycomb, and fascial patterns at biopsy sites correlated with inflammatory cell infiltration in the endomysium (OR 11.9, p= 0.005), perimysium (OR 6.0, p= 0.014), and fascia (OR 16.9, p< 0.001), respectively. Honeycomb and foggy patterns were characteristic of patients with anti-TIF1γ or anti-Mi2 antibodies and MSA-negative dermatomyositis, and those with anti-SRP or anti-HMGCR antibodies and MSA-negative polymyositis (PM), respectively. The honeycomb pattern positively correlated with malignancy (OR 6.87, p< 0.001) and Gottron sign (OR 8.05, p= 0.002); the foggy pattern correlated with muscle weakness (OR 11.24, p= 0.005). The dense dot pattern was associated with dysphagia (OR 6.27, p= 0.006) and malignancy (OR 8.49, p= 0.002). CONCLUSION: Muscle MRI holds promise in predicting muscle pathology, disease subtypes, and clinical manifestations of IIMs.

Anti-PL-7, anti-Ro/SSA, anti-Mi-2, and anti-TIF1-γ correlate with specific patterns of histopathologic features in dermatomyositis: An analysis of 39 skin biopsy specimens from 25 patients.

BACKGROUND: In dermatomyositis (DM), myositis-specific and myositis-associated antibodies have been correlated with clinical features. It is unknown if histopathologic findings in lesional skin biopsies correlate with serologic subtypes of DM. METHODS: A retrospective chart review of patients with DM was performed. Patients with myositis antibodies and DM lesional skin biopsies were included in the study. Skin biopsies were reviewed by blinded dermatopathologists for 20 histopathologic features. RESULTS: There was a statistically significant (p < 0.05) association between anti-PL-7 serology and decreased degree of vacuolar degeneration, necrotic keratinocytes, and thickening of the epidermal basement membrane. Anti-aminoacyl tRNA synthetase (anti-ARS) antibodies had the same significant negative association with degree of vacuolar degeneration, necrotic keratinocytes, and thickening of the epidermal basement membrane. A similar pattern was seen with an anti-cytoplasmic serology; where there was a significant association with an increased degree of vacuolar degeneration and necrotic keratinocytes, and a nonsignificant trend of minimally thickened epidermal basement membrane. There was a statistically significant association between anti-Ro/SSA serology and increased degree of vacuolar degeneration. Anti-TIF1-γ serology was significantly associated with the increased presence of necrotic keratinocytes and pigment incontinence, and displayed a pattern of increased neutrophils. There was a significant association between anti-Mi-2 antibodies and pigment incontinence, as well as between myositis-specific antibodies and pigment incontinence. A statistically significant positive association was found between nuclear antibodies and degree of vacuolar degeneration, thickened epidermal basement membrane, pigment incontinence, and epidermal atrophy. CONCLUSION: In patients with DM, some specific serotypes, including anti-PL-7, anti-Ro/SSA, anti-Mi-2, and anti-TIF1-γ, may have characteristic histopathologic features.

Myositis autoantibodies detected by line blot immunoassay: clinical associations and correlation with antibody signal intensity.

The aim of this study is to assess the relationship between myositis specific (MSA) and myositis associated (MAA) antibodies and diagnosis (including idiopathic inflammatory myopathies [IIM] and other systemic autoimmune diseases [SAID]), and to explore the impact of antibody signal intensity in diagnostic accuracy. We retrospectively reviewed all the serum samples obtained from patients tested for MSA/MAA by line immunoassay (LIA) between 01/01/2018 and 31/12/2020 in Ramón y Cajal University Hospital (Spain). Clinical true positive (CTP) MSAs and MAAs were defined as those patients with IIM or SAID with phenotypes expected of that MSA/MAA. Patients who did not have a phenotype compatible with that antibody were classified as clinical false positive (CFP). One hundred and thirty positive samples were analysed. Forty-six patients (33.38%) were classified as IIM, forty-two (32.3%) as SAID and forty-two (32.3%) as non-IIM/SAID. Among these 130 patients, 164 MSA/MAA were detected. Eighty-five (51.8%) positive MSA/MAA were classified as CTP, and seventy-nine (48.2%) as CFP. Strongly positive antibodies were more frequently CTP (35/47, 74.5%) than weak positives (54/68, 36.8%), (p ˂ 0.001). Antibodies classified as CTP had a higher signal intensity than CFP (36.77 AU vs 20.00 AU, CI95% 7.79-22.09, p ˂ 0.001). The probability of a CFP was associated to negative ANA, low ANA titer, and multiple positive MSA/MAA (p Ë‚ 0.001). In this study, we confirmed that CFP results using LIA are frequent, and are associated with low signal intensity MSA/MAA, negative ANA, lower titer ANA, and with multiple positive samples.

Anti-nuclear matrix protein 2 antibody-positive inflammatory myopathies represent extensive myositis without dermatomyositis-specific rash.

OBJECTIVES: Myositis-specific autoantibodies (MSAs) define distinct clinical subsets of idiopathic inflammatory myopathies (IIMs). The anti-nuclear matrix protein 2 (NXP2) antibody, a MSA detected in juvenile/adult IIMs, has been reported to be associated with a high risk of subcutaneous calcinosis, subcutaneous oedema and internal malignancies. The study aimed to clarify the clinical features of anti-NXP2 antibody-positive IIMs in detail. METHODS: This was a multicentre retrospective observational study on 76 anti-NXP2 antibody-positive patients. The antibody was detected via a serological assay using immunoprecipitation and western blotting. The patients were selected from 162 consecutive Japanese patients with IIMs. RESULTS: The cohort of anti-NXP2 antibody-positive IIMs included 29 juvenile patients and 47 adult patients. Twenty-seven (35.5%) patients presented with polymyositis phenotype without dermatomyositis-specific skin manifestations (heliotrope rash or Gottron sign/papules); this was more common in the adults than children (48.9% vs 15.8%, P < 0.01). Nine (11.8%) patients had subcutaneous calcinosis, and 20 (26.3%) patients had subcutaneous oedema. In addition, the proportion of patients with muscle weakness extending to the distal limbs was high (36 patients [47.4%]) in this cohort. Adult patients had a higher prevalence of malignancy than the general population (age-standardized incidence ratio of malignancies: 22.4). CONCLUSION: Anti-NXP2 antibody-positive IIMs, which include dermatomyositis sine dermatitis, are characterized by atypical skin manifestations and extensive muscular involvement.

Update on Cutaneous Signs to Assist in the Diagnosis of Dermatomyositis.

PURPOSE OF REVIEW: Dermatomyositis (DM) is a heterogeneous idiopathic inflammatory myopathy that can be challenging to diagnose. Learning about the cutaneous manifestations in DM can assist with prompt diagnosis as well as subgroup classification. This review highlights recent data regarding cutaneous signs in DM and their associations with myositis-specific antibodies (MSAs). RECENT FINDINGS: Several novel DM skin signs have recently been reported. Novel and confirmatory data have helped to define more clearly the associations between various cutaneous manifestations and MSAs. Awareness of the diverse cutaneous phenotypes can help with the timely diagnosis of DM. As some MSAs are associated with atypical skin features and/or characteristic patterns of clinical findings, knowledge of these associations can help clinicians to recognize DM patients. Understanding how the prevalence and presentation of various cutaneous signs differ among ethnically diverse patients is a high priority for further study.

Treatment challenges in clinically amyopathic dermatomyositis: A case series and review of new therapeutic options for skin involvement.

The term clinically amyopathic dermatomyositis (CADM) is used to represent a subgroup of patients with the typical cutaneous features of dermatomyositis (DM) in the absence of muscle involvement. Similar to classic DM, CADM can be associated with other connective tissue disorders and systemic manifestations such as interstitial lung disease and malignancy. Owing to the frequent discordance between muscle response and skin disease, the therapeutic approach to CADM represents a challenge. The current literature suggests that CADM treatment should follow a specific protocol, influenced by visceral involvement and the expression of certain myositis-specific antibodies, and different from the recommendation in the presence of myositis. Here, we present five new cases of CADM. We describe the available therapeutic options for skin manifestations in this type of DM, and we propose a step-by-step therapeutic scheme, using the cutaneous dermatomyositis disease area and severity index to assess response. Our literature review establishes mycophenolate mofetil and intravenous immunoglobulin as the most frequently successful therapies in refractory skin disease.

Interstitial lung disease is a dominant feature in patients with circulating myositis-specific antibodies.

BACKGROUND: Many patients with polymyositis (PM) or dermatomyositis (DM) have circulating myositis-specific antibodies (MSAs). Interstitial lung disease (ILD) is a common manifestation of PM/DM, and it can even precede the onset of characteristic muscle or skin manifestations. Furthermore, there appear to be some patients with ILD and circulating MSAs who do not develop muscle or skin disease even after prolonged follow-up. We sought to determine whether ILD is equally or more common than myositis or dermatitis at the time of initial detection of MSAs. METHODS: We identified all patients found to have circulating MSAs at our institution over a 4-year period and assessed for the presence of lung, muscle, and skin disease at the time of initial detection of MSAs. Among those found to have ILD, we compared demographic and clinical features, chest CT scan findings, and outcomes between those with PM/DM-associated ILD and those with ILD but no muscle or skin disease. RESULTS: A total of 3078 patients were tested for MSAs, and of these 40 were positive. Nine different MSAs were detected, with anti-histidyl tRNA synthetase (anti-Jo-1) being the most common (35% of MSAs). Among patients with positive MSAs, 86% were found to have ILD, compared to 39% and 28% with muscle and skin involvement, respectively (p < 0.001). Fifty percent of all MSA-positive patients had isolated ILD, with no evidence of muscle or skin disease. Those with isolated ILD were more likely to be older and have fibrotic changes on chest CT, less likely to receive immunomodulatory therapy, and had worse overall survival. CONCLUSIONS: In this study we found that individuals with circulating MSAs were more likely to have ILD than classic muscle or skin manifestations of PM/DM at the time of initial detection of MSAs. Our findings suggest that the presence of ILD should be considered a disease-defining manifestation in the presence of MSAs and incorporated into classification criteria for PM/DM.

[Long-term rituximab treatment of refractory idiopathic inflammatory myopathy: A report of 3 cases].

Idiopathic inflammatory myopathies are a group of rare but serious diseases. The treatment of refractory idiopathic inflammatory myopathy is always challenging, especially in children. Three cases of refractory idiopathic inflammatory myopathy treated by rituximab were reported and discussed with the review of relevant literature. All were female with on-set age of 8 years and 6 months, 11 years and 7 months, 4 years and 2 months old, respectively. All had acute onset, presenting with progressive and severe muscle weakness. All lost ambulation within 1 or 2 months, with difficult swallowing and low voice. Respiratory distress occurred in case 2 after an attack of asphyxia due to an aspiration of sputum, and ventilator support was required for 1 month. Rashes were detected at the initial stage of the disease in cases 2 and 3. Patient 2 showed facial erythematous papules, spreading to her neck and hands. Patient 3 showed purplish eyelids with peri-orbital swelling, generalized edema involving all her limbs. Creatine kinase (CK) levels were markedly elevated in all the patients, ranging from 6 000 IU/L to 28 819 IU/L. Anti-SRP antibody was identified in cases 1, and anti-NXP2 antibodies were confirmed in cases 2 and 3. MRI of both thighs in all the patients showed profound muscle and fascial edema. Muscle pathology of patient 1 showed prominent fiber variation and endomysial fibrosis, with overexpression of MHC-Ⅰ. While muscle pathology in patients 2 and 3 showed scattered fiber necrosis, regeneration, endomysial edema without inflammatory cell infiltration. All the patients were diagnosed with idiopathic inflammatory myopathy and failed to the initial treatment including adequate glucocorticoids and high-dose immunoglobulin therapy. Other immunosuppressants (methotrexate, cyclophosphamide) were also tried in cases 2 and 3 with poor response. Then all the patients were treated with rituximab combined with glucocorticoids. Patient 1 regained normal strength and discontinued rituximab at the end of her last follow-up (2 years and 7 mouths). Though calcinosis developed during the follow-up period, significant improvement was noticed in cases 2 and 3 (both regained the ability to walk independently) at the end of their last follow-up after 2 years and 8 months, 3 years and 2 months respectively. Long-term rituximab therapy may improve the prognosis of refractory idiopathic inflammatory myopathy, especially with positive anti-SRP and anti-NXP2 antibodies.

Dermatomyositis: Clinical features and pathogenesis.

Dermatomyositis (DM) is an idiopathic inflammatory myopathy that is clinically heterogeneous and that can be difficult to diagnose. Cutaneous manifestations sometimes vary and may or may not parallel myositis and systemic involvement in time course or severity. Recent developments in our understanding of myositis-specific antibodies have the potential to change the diagnostic landscape of DM for dermatologists. Although phenotypic overlap exists, anti-Mi2, -MDA5, -NXP2, -TIF1, and -SAE antibodies may be correlated with distinct DM subtypes in terms of cutaneous manifestations, systemic involvement, and malignancy risk. This review highlights new findings on the DM-specific myositis-specific antibodies and their clinical associations in both adults and children.

Benign acute viral myositis in African migrants: A clinical, serological, and pathological study.

BACKGROUND: Several viruses have been described as causes of acquired inflammatory myopathies; however, the mechanisms by which they cause muscle disease are still unclear. The aim of this study was to describe the laboratory features of benign acute myositis in a small case series. METHODS: A detailed pathological and serological analysis was performed in five African migrants who developed an acute viral myositis complicated by rhabdomyolysis. RESULTS: Muscle biopsies clearly documented an inflammatory myopathy with histological features similar to polymyositis including CD8+ T cells surrounding and invading nonnecrotic muscle fibers, CD68+ macrophages and major histocompatibility complex class I antigen upregulation. In addition, positivity for myositis-specific antibodies (MSA), in particular anti-aminoacyl tRNA synthetases, was found in the serum of two patients. CONCLUSIONS: Our study demonstrated that T-cell mediated injury occurs in muscle of patients with acute viral myositis, and that MSA may be present in the serum of these patients.

Prevalence of Myositis-Specific Antibodies in Idiopathic Interstitial Pneumonias.

Although included in the serological domain of the 'interstitial pneumonia with auto-immune features' (IPAF) research statement, the search for myositis-specific antibodies (MSA) is not incorporated in routine clinical practice. The objective of the study was to evaluate MSA prevalence in an idiopathic interstitial pneumonia (IIP) cohort (n = 68) with suggestive morphological interstitial lung disease patterns. Twelve of 68 patients (17.6%) carried MSA, whereof only two were anti-nuclear antibody-positive. Besides female gender, no demographic or pulmonary function parameter was predictive for MSA positivity. MSA were present in 32.4% of IPAF patients (n = 37), being essential for IPAF diagnosis in four of them (10.8%).

[Myositis-specific antibodies associated with juvenile dermatomyositis]. / Myositisspezifische Antikörper bei juveniler Dermatomyositis.

BACKGROUND: Juvenile dermatomyositis (JDM) is a rare autoimmune disease associated with typical skin changes and muscle weakness. Within the framework of the diagnostics, myositis-associated (MAA) and myositis-specific antibodies (MSA) can be detected. These are important for the assessment of the course of the disease and the prognosis. METHOD: In this study we searched for MAA and MSA by means of a line immunoassay in 12 currently supervised JDM patients in the Rheumatism Center Sankt Augustin. RESULTS: In 10 of the 12 patients a total of 15 myositis antibodies were detected where 3 patients each had Mi2, SRP or NXP2 antibodies, 2 had TIF-1γ antibodies and Jo1 or Mi2ß antibodies were found in 1 patient each. Of the patients two had additional PM-Scl antibodies. In the 10 patients with detected antibodies, a good phenotype-serotype correlation was found with deviation from the phenotypes described in the literature in only 3 patients. CONCLUSION: The frequent detection of certain antibodies and the good correlation with those phenotypes described in the literature, show that the determination of MSA is an important diagnostic tool to assess the course, complications and outcome and to initiate adequate therapy at an early stage.

[Current update on dermatomyositis]. / Aktuelle Aspekte zur Dermatomyositis.

Dermatomyositis (DM) is a rare autoimmune disease with involvement of skin and muscle that is classified as an idiopathic inflammatory myopathy. In addition to cutaneous lesions as well as weakness and atrophy of muscles, the heart and lungs are the major affected organs. DM occurs in association with malignant tumors in 20% of affected adults. The pathogenesis of the disease is not completely understood. DM is a multifactorial disease influenced by genetic, environmental and immunological factors. The immune response is characterized by activation of innate and adaptive immune mechanisms and a strong activation of the type I interferon pathway. Myositis-specific antibodies are characteristic of DM and allow differential diagnosis. Therapies include corticosteroids, antimalarials, immunoglobulins, biologics such as rituximab or JAK inhibitors. Early diagnosis and treatment are essential for the prognosis.

High Prevalence of Myositis-Specific and Associated Antibodies in Patients with Pulmonary Hypertension.

Pulmonary hypertension (PH) is a serious condition linked to immune-system dysfunction. Myositis-specific/associated antibodies (MSAs/MAAs) play a role in idiopathic inflammatory myopathy (IIM) and interstitial lung disease (ILD), but their significance in PH remains unclear. We believe the presence of these antibodies may be underestimated. This study analyzed adult PH patients without pre-existing IIM for MSA/MAA prevalence using a line-blot assay. We compared PH patients with and without ILD signs to a cohort clinically suspected of IIM/ILD (n = 558). Our PH cohort (n = 121) showed a significantly higher prevalence of overall weak positive MSAs/MAAs and positive overlap syndrome-associated MAAs than the suspected IIM/ILD group (p < 0.001). Notably, MSAs/MAAs were found in PH patients both with and without ILD, though more prevalent in those with ILD. Anti-synthetase and anti-overlap syndrome antibodies were the most common. Our study is the first to systematically show a high MSA/MAA prevalence in PH without IIM presentation. This highlights the need to consider PH when diagnosing MSA/MAA-associated conditions. We recommend MSA/MAA screening for newly diagnosed PH, especially in those with ILD, for early detection and potential immunomodulatory treatment. Further research should explore the link between MSAs/MAAs and PH, and the value of monitoring patients with weak MSA/MAA positivity over time.

What should we expect when two myositis-specific antibodies coexist in a patient.

BACKGROUND: The coexistence of two myositis-specific autoantibodies (MSA) is considered extremely rare. We describe three patients with both anti-signal recognition particle (SRP) antibodies and another MSA in serum. METHODS: We performed a retrospective clinical data collection and follow-up studies of the clinical manifestations and treatment outcome of three patients positive with anti-SRP antibodies and other MSAs. IgG antibodies against MSAs were detected using commercial line immunoblot assay. RESULTS: The tests of MSA showed positive result of anti-SRP antibodies and another one MSA including anti-TIF1-γ, anti-Jo1, or anti-EJ antibodies, respectively. The proximal muscle weakness appeared in 2 patients; interstitial lung disease presented in 2 patients. The serum CK level was elevated in 1 patient. The muscle biopsy showed necrotizing myopathy in 1 patient and deposition of membrane attack complex on scattered myofibers in the other one patient. One of the two patients with interstitial lung disease died because of respiratory failure. One patient had completely improved and the other one showed partial remission after immunosuppressive therapy. CONCLUSIONS: The patients with anti-SRP antibodies co-occurred with the other MSA may have various clinical characteristics. The clinicopathological phenotypes of these patients seem to be mainly caused by one of the MSAs, namely the responsible antibody.

Detection of Myositis Autoantibodies by Multi-Analytic Immunoassays in a Large Multicenter Cohort of Patients with Definite Idiopathic Inflammatory Myopathies.

BACKGROUND: The usefulness of myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs) for the assessment of idiopathic inflammatory myopathies (IIMs) is acknowledged, but laboratory standardization remains a challenge. We detected MSAs/MAAs by multi-analytic line immunoassay (LIA) and particle-based multi-analyte technology (PMAT) in a multicenter cohort of patients with IIMs. METHODS: We tested the sera from 411 patients affected with definite IIM, including 142 polymyositis (PM), 147 dermatomyositis (DM), 19 cancer-associated myositis, and 103 overlap myositis syndrome (OM), and from 269 controls. MSAs/MAAs were determined by 16Ags LIA in all sera, and anti-HMGCR by ELISA in 157/411 IIM sera and 91/269 control sera. The analytical specificity of LIA/HMGCR ELISA was compared with that of PMAT in 89 MSA+ IIM sera. RESULTS: MSAs/MAAs were positive in 307/411 (75%) IIM patients and 65/269 (24%) controls by LIA (Odds Ratio 9.26, 95% CI 6.43-13.13, p < 0.0001). The sensitivity/specificity of individual MSAs/MAAs were: 20%/100% (Jo-1), 3%/99.3% (PL-7), 4%/98.8% (PL-12), 1%/100% (EJ), 0.7%/100% (OJ), 9%/98% (SRP), 5.6%/99.6% (TIF1γ), 4.6%/99.6% (MDA5), 8%/96% (Mi-2), 1.5%/98% (NXP2), 1.7%/100% (SAE1), 4%/92% (Ku), 8.5%/99% (PM/Scl-100), 8%/96% (PM/Scl-75), and 25.5%/79% (Ro52). Anti-HMGCR was found in 8/157 (5%) IIM patients and 0/176 (0%) controls by ELISA (p = 0.007). Concordance between LIA/HMGCR ELISA and PMAT was found in 78/89 (88%) samples. Individual MSAs detected by LIA were associated with IIM subsets: Jo-1 with PM and OM, PL-12 with OM, Mi-2, TIF1γ, and MDA5 with DM, SRP with PM, and PM/Scl-75/100 with OM (p < 0.001 for all). CONCLUSIONS: Since MSAs are mostly mutually exclusive, multi-specific antibody profiling seems effective for a targeted clinical-serologic approach to the diagnosis of IIMs.

Myositis-Specific and Myositis-Associated Antibodies in Fibromyalgia Patients: A Prospective Study.

Fibromyalgia (FM) is a common rheumatologic disorder characterised by widespread muscular pain. Myalgia is also a common clinical feature in Connective Tissue Disease (CTD), and FM should be studied for the concomitant presence of a CTD. The aim of this study is to evaluate the prevalence of Myositis-Specific and Myositis-Associated Antibodies (MSA/MAA) in a cohort of FM patients. We enrolled 233 consecutive FM patients (defined according to the 2016 criteria) that did not report clinical signs of autoimmune disorders and followed them for at least one year. The patients were tested for MSA/MAA with immunoblotting. FM patients were seropositive for Antinuclear Antibodies (ANA) in 24% of cases, for MSA in 9%, and for MAA in 6%. A specific diagnosis of CTD was made in 12 patients (5.2%), namely, 5 cases of primary Sjögren's Syndrome and 7 of Idiopathic Inflammatory Myopathy. Seropositive patients showed clinical features similar to those who were seronegative at baseline. A CTD diagnosis was associated with ANA positivity (p = 0.03, X2 4.9), the presence of a speckled pattern (p = 0.02, X2 5.3), positivity for MAA (p = 0.004, X2 8.1), and MSA (p = 0.003, X2 9.2). In conclusion, a non-negligible proportion of FM patients may be seropositive for MSA/MAA, and that seropositivity might suggest a diagnosis of CTD.

Nailfold capillary density in 140 untreated children with juvenile dermatomyositis: an indicator of disease activity.

BACKGROUND: We lack a reliable indicator of disease activity in Juvenile Dermatomyositis (JDM), a rare disease. The goal of this study is to identify the association of nailfold capillary End Row Loop (ERL) loss with disease damage in children with newly diagnosed, untreated JDM. FINDINGS: We enrolled 140 untreated JDM and 46 age, race and sex matched healthy controls, ages 2-17. We selected items from the Juvenile Myositis Registry for analysis. Variables include average ERL density of 8 fingers, average capillary pattern, hemorrhages, and clinical and laboratory correlates. Laboratory data includes Myositis Specific Antibodies (MSA), disease activity scores (DAS), Childhood Myositis Assessment Scale (CMAS), and standard clinical serologic data. The reduced mean ERL density is 5.1 ± 1.5/mm for untreated JDM vs 7.9 ± 0.9/mm for healthy controls, p < 0.0001, and is associated with DAS-skin, r = -0.27 p = 0.014, which did not change within the age range tested. Untreated JDM with MSA Tif-1-γ had the lowest ERL density, (p = 0.037); their ERL patterns were primarily "open" and the presence of hemorrhages in the nailfold matrix was associated with dysphagia (p = 0.004). CONCLUSIONS: Decreased JDM ERL density is associated with increased clinical symptoms; nailfold hemorrhages are associated with dysphagia. Duration of untreated disease symptoms and MSA, modify NFC shape. We speculate nailfold characteristics are useful indicators of disease activity in children with JDM before start of therapy.