Anti-PM/Scl antibody-positive dermatomyositis in a Japanese patient: a case report and review of the literature

Clinical Significance of Antinucleolar Antibodies: Biomarkers for Autoimmune Diseases, Malignancies, and others

Nucleolar staining is one of the standard patterns in immunofluorescence antinuclear antibodies (ANA), seen in 5-9% of ANA in various conditions. Antinucleolar antibodies (ANoA) are classified into 3 patterns in the International Consensus on ANA Patterns (ICAP) classification; AC-8 homogeneous pattern, AC-9 clumpy pattern, and AC-10 punctate pattern. Specificities known to show AC-8 include anti-Th/To, -PM-Scl, -nucleophosmin/B23, -nucleolin/C23, -No55, and others. AC-9 is seen by anti-fibrillarin/U3RNP and AC-10 by anti-RNA polymerase I and hUBF/NOR-90. ANoA has been classically known to be associated with scleroderma (SSc) and the characterization of nucleolar antigens identified several autoantigens recognized by SSc autoantibodies. The clinical association of anti-Th/To, PM-Scl, fibrillarin/U3RNP, and RNA polymerase I with SSc or SSc-overlap syndrome is well established, and commercial assays are developed. Anti-hUBF/NOR90, nucleophosmin/B23, and nucleolin/C23 are known for decades and reported in systemic autoimmune rheumatic diseases (SARDs), malignancies, graft versus host disease (GVHD), and others; however, their clinical significance remains to be established.

Interstitial Lung Disease Is a Major Characteristic of Patients Who Test Positive for Anti-PM/Scl Antibody

Objective

This study aimed to analyze the clinical features of anti-PM/Scl antibodies in Chinese patients.

Method

We reviewed the clinical data of anti-PM/Scl antibody-positive patients, including their long-term follow-up.

Results

A total of 30 patients carried anti-PM/Scl antibodies, 21 (70%) were females, and the mean age was 55.4 years, 15 (50%) and 10 (33.3%) patients were positive for anti-PM/Scl-75 and anti-PM/Scl-100, respectively. Fifteen cases (50%) were diagnosed as inflammatory myopathy, namely, 11 dermatomyositis (DM) and 4 polymyositis (PM). Five (16.7%) patients were diagnosed with overlap syndrome, and only one (3.3%) was diagnosed as systemic sclerosis. The other 9 (30%) patients were classified as undifferentiated connective tissue disease. Twenty-six (86.7%) had interstitial lung disease (ILD) and was the sole manifestation in 8 (26.7%) patients, 15 (58.0%) showed non-specific interstitial pneumonia based on high-resolution CT or lung biopsy. The majority of patients (95%) with mild and moderate groups on basis of pulmonary function tests. Compared to the anti-PM/Scl-100 group, the occurrence of clinical characteristics was not significantly different from the anti-PM/Scl-75 group, except the levels of C-reactive protein and erythrocyte sedimentation rate in the anti-PM/Scl-75 antibody-positive group were higher (p < 0.05). All patients with positive Ro-52 antibodies had ILD and were more likely to develop skin rash in the group with Ro-52 (p = 0.024). With a follow-up of the present cohort, 70.8% improved with treatment, but 16.7% of patients are easy to relapse.

Conclusion

The anti-PM/Scl antibody occurred frequently in DM/PM patients, ILD was the major clinical feature, especially in patients combined with Ro-52. Some patients may complicate with ILD alone without extrapulmonary manifestations. Anti-PM/Scl antibodies positive patients were responsive to treatment.

A Japanese Patient with Anti-PM/Scl and Centromere Antibody-Positive Scleroderma-Amyopathic Dermatomyositis Overlap Syndrome Who Developed Renal Crisis

Anti-PM/Scl antibodies are associated with the overlap syndrome of systemic sclerosis and dermatomyositis/polymyositis (SSc-DM/PM), and are found in 50% of SSc-DM/PM cases in Europe and the United States, whereas they are rare in Japan. We report a case of an 80-year-old Japanese female with SSc-amyopathic dermatomyositis (ADM) overlap syndrome, who developed scleroderma renal crisis (SRC), a complication of SSc. She had positive antinuclear antibodies in a discrete-speckled and nucleolar pattern and anticentromere antibodies and anti-PM/Scl antibodies were confirmed by ELISA and immunoprecipitation, respectively. The incidence rate of SRC in SSc patients varies significantly depending on the specificity of autoantibodies, with the highest incidence of ~50% in anti-RNA polymerase III antibody positive patients, followed by ~10% in anti-PM/Scl and lower incidence of 0.45% in anticentromere antibody-positive cases. Anti-PM/Scl antibodies are uncommon in Japanese patients presumably due to its strong association with certain HLA haplotype that is rare in Japanese. Clinical significance of anti-PM/Scl antibodies in Japanese patients will need to be clarified with accumulation of cases in future studies.

An Anti-PM/Scl-75 Antibody-positive Japanese Woman Who Developed Inflammatory Myopathy

A 69-year-old Japanese woman presented with mild muscle weakness of the neck and symmetrical proximal parts of the upper and lower limbs. Laboratory tests, needle electromyography, and a muscle biopsy revealed inflammatory myopathy with an apparent clinical classification of polymyositis and positive findings for anti-PM/Scl-75 antibody. This antibody is rare among Japanese populations, and most Japanese patients with the antibody are not classified with the inflammatory myopathy seen in polymyositis. The muscle biopsy also showed marked necrotic and regenerative fibers. We need to collectively investigate patients with the potential to develop this disease, and to identify any unique characteristics for Asian populations, including Japanese.