PCP chemoprophylaxis is essential for lymphopenic dermatomyositis patients treated with immunomodulators

The RIG-I pathway is involved in peripheral T cell lymphopenia in patients with dermatomyositis

BACKGROUND

Peripheral T cell lymphopenia is a clinical phenomenon in some patients with dermatomyositis (DM). Patients with T cell lymphopenia are more susceptible to life-threatening infections. However, the pathogenesis of T cell lymphopenia remains unclear. In this study, we aimed to determine retinoic acid-inducible gene I (RIG-I) expression in peripheral T lymphocytes and explore the correlation between RIG-I and T cell lymphopenia in DM.

METHODS

The mRNA and protein expression levels of RIG-I were determined in peripheral T lymphocytes of 26 treatment-naive DM patients by q-PCR and Western blot. The apoptosis of peripheral T lymphocytes was detected by flow cytometry. The associations between RIG-I expression levels and clinical characteristics were investigated. In Jurkat cell, we examined the relationship between RIG-I and cell apoptosis following RIG-I overexpression or activation by specific ligand (pppRNA). The CRISPR/Cas9 gene editing system was used for RIG-I knockout. Fas and caspase 3 were identified by Western blot. CCK8 colorimeter was performed to monitor cell proliferation.

RESULTS

In DM patients, we observed the peripheral T lymphocyte count decreased notably while the apoptosis of T lymphocytes increased significantly compared with healthy control. RIG-I expression levels in peripheral T cell correlated negatively with T cell count in DM patients. RIG-I protein expression decreased significantly, and the number of T cell increased when disease was improved. In Jurkat cells, increased apoptosis and elevated expression of Fas and cleaved-caspase 3 protein were observed following RIG-I overexpression or RIG-I-specific ligand (pppRNA) activation. Meanwhile, the proliferation of Jurkat cells was markedly reduced. Whereas, neither cell apoptosis nor the cell viability of the RIG-I knockout clones exhibited significant changes following pppRNA activation.

CONCLUSION

Our study showed for the first time that negative correlation between the increased RIG-I expression in peripheral T lymphocyte and T cell count in some patients with DM. We demonstrated that highly expressed RIG-I played a critical role in inducing apoptosis and inhibiting proliferation of T lymphocyte in vitro. Therefore, RIG-I-mediated apoptosis may be one of the possible mechanisms of T cell lymphopenia in some patients with DM. These findings expand our existing knowledge on the mechanisms of innate immunity in pathogenesis and provide new therapeutic avenues for DM.

Autoimmune Myopathies: Updates on Evaluation and Treatment

The major forms of autoimmune myopathies include dermatomyositis (DM), polymyositis (PM), myositis associated with antisynthetase syndrome (ASS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). While each of these conditions has unique clinical and histopathological features, they all share an immune-mediated component. These conditions can occur in isolation or can be associated with systemic malignancies or connective tissue disorders (overlap syndromes). As more has been learned about these conditions, it has become clear that traditional classification schemes do not adequately group patients according to shared clinical features and prognosis. Newer classifications are now utilizing myositis-specific autoantibodies which correlate with clinical and histopathological phenotypes and risk of malignancy, and help in offering prognostic information with regard to treatment response. Based on observational data and expert opinion, corticosteroids are considered first-line therapy for DM, PM, ASS, and IMNM, although intravenous immunoglobulin (IVIG) is increasingly being used as initial therapy in IMNM related to statin use. Second-line agents are often required, but further prospective investigation is required regarding the optimal choice and timing of these agents.

Infections and the relationship to treatment in neuromuscular autoimmunity

INTRODUCTION

This study aimed to identify infections in patients with myasthenia gravis, dermatomyositis, and chronic inflammatory demyelinating polyradiculoneuropathy, and to investigate the relationship between infection and immunomodulation.

METHODS

A retrospective chart review examined 631 patients with myasthenia gravis (n = 358), chronic inflammatory demyelinating polyradiculoneuropathy (n = 124), and dermatomyositis (n = 149) patients over a 10-year time period.

RESULTS

Infection rates were similar at approximately 19% in all 3 diseases. Of the infections in which a causative organism was identified, pneumonia, sepsis, and opportunistic infections were the leading diagnoses. A multivariate model demonstrated a significant association between infection and an increased dose of plasma exchange, mycophenolate mofetil, and corticosteroid therapy.

DISCUSSION

There are few large studies investigating rates of infections in patients with autoimmune neuromuscular disorders and the relationship to immunomodulation. This study not only demonstrates the remarkably similar infection rates across the 3 diseases studied, but also shows their relationship to commonly used immunotherapies. Muscle Nerve 57: 927-931, 2018.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIM) consist of rare heterogeneous autoimmune disorders that present with marked proximal and symmetric muscle weakness, except for distal and asymmetric weakness in inclusion body myositis. Despite many similarities, the IIM are fairly heterogeneous from the histopathologic and pathogenetic standpoints, and also show some clinical and treatment-response differences. The field has witnessed significant advances in our understanding of the pathophysiology and treatment of these rare disorders. This review focuses on dermatomyositis, polymyositis, and necrotizing myopathy, and examines current and promising therapies.

Red fist and muscle weakness with a rare complication

A 64-year-old man was referred to our hospital, for a second opinion, with fever, skin lesions and general muscle pain. He has been treated in another hospital with antibiotics on suspicion of erysipelas. A week later skin lesions developed on the metacarpophalangeal and proximal carpophalangeal joints of the hands and nose. His mobility was impaired due to muscle pain and muscle weakness. He also showed proximal muscle atrophy and most importantly a typical heliotrope rash in the eyes. Based on these clinical observations, the most likely diagnosis was dermatomyositis. The diagnosis was confirmed by the presence of increased serum creatine kinase levels and abnormalities in skin and muscle biopsy. Prednisone (70 mg/kg) was initiated, but after 19 days the patient developed a Pneumocystis jiroveci pneumonia. He died of respiratory failure a few days later.