Inclusion body myositis in the rheumatology clinic

Epidemiology of the idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic autoimmune diseases that affect the skeletal muscles and can also involve the skin, joints, lungs and heart. The epidemiology of IIM is obscured by changing classification criteria and the inherent shortcomings of case identification using healthcare record diagnostic coding. The incidence of IIM is estimated to range from 0.2 to 2 per 100,000 person-years, with prevalence from 2 to 25 per 100,000 people. Although the effects of age and gender on incidence are known, there is only sparse understanding of ethnic differences, particularly in indigenous populations. The incidence of IIM has reportedly increased in the twenty-first century, but whether this is a genuine increase is not yet known. Understanding of the genetic risk factors for different IIM subtypes has advanced considerably. Infections, medications, malignancy and geography are also commonly identified risk factors. Potentially, the COVID-19 pandemic has altered IIM incidence, although evidence of this occurrence is limited to case reports and small case series. Consideration of the current understanding of the epidemiology of IIM can highlight important areas of interest for future research into these rare diseases.

Long-term safety of COVID vaccination in individuals with idiopathic inflammatory myopathies: results from the COVAD study

Limited evidence on long-term COVID-19 vaccine safety in patients with idiopathic inflammatory myopathies (IIMs) continues to contribute to vaccine hesitancy. We studied delayed-onset vaccine adverse events (AEs) in patients with IIMs, other systemic autoimmune and inflammatory disorders (SAIDs), and healthy controls (HCs), using data from the second COVID-19 Vaccination in Autoimmune Diseases (COVAD) study. A validated self-reporting e-survey was circulated by the COVAD study group (157 collaborators, 106 countries) from Feb-June 2022. We collected data on demographics, comorbidities, IIM/SAID details, COVID-19 history, and vaccination details. Delayed-onset (> 7 day) AEs were analyzed using regression models. A total of 15165 respondents undertook the survey, of whom 8759 responses from vaccinated individuals [median age 46 (35-58) years, 74.4% females, 45.4% Caucasians] were analyzed. Of these, 1390 (15.9%) had IIMs, 50.6% other SAIDs, and 33.5% HCs. Among IIMs, 16.3% and 10.2% patients reported minor and major AEs, respectively, and 0.72% (n = 10) required hospitalization. Notably patients with IIMs experienced fewer minor AEs than other SAIDs, though rashes were expectedly more than HCs [OR 4.0; 95% CI 2.2-7.0, p < 0.001]. IIM patients with active disease, overlap myositis, autoimmune comorbidities, and ChadOx1 nCOV-19 (Oxford/AstraZeneca) recipients reported AEs more often, while those with inclusion body myositis, and BNT162b2 (Pfizer) recipients reported fewer AEs. Vaccination is reassuringly safe in individuals with IIMs, with AEs, hospitalizations comparable to SAIDs, and largely limited to those with autoimmune multimorbidity and active disease. These observations may inform guidelines to identify high-risk patients warranting close monitoring in the post-vaccination period.

Cricopharyngeal bar and dermatomyositis: A cause of rapidly progressive dysphagia

BACKGROUND

Idiopathic inflammatory myopathies (IIM) are immune-mediated conditions that affect striated muscle, and are frequently associated with dysphagia. Dysphagia in these cases can be due to weakness of the muscles involved in swallowing or the presence of restrictive pharyngeal defects, such as cricopharyngeal bars. Treatment of dysphagia in IIM revolves around immunosuppressive therapies, and procedures to disrupt cricopharyngeus muscle when immunosuppressive therapies are unsuccessful.

CASE REPORT

A 73-year-old female presented with rapidly progressive proximal muscle weakness and dysphagia to the point she could not swallow liquids or solids. She had a rash over the extensor surfaces of the limbs, and periorbital-edema. Her creatine kinase was elevated, and skin biopsy showed an interface inflammatory reaction; however, myositis line assay revealed no autoantibodies, and a muscle biopsy was unremarkable. She was diagnosed with dermatomyositis with life-threatening dysphagia, and was admitted to our institution and treated with corticosteroids, methotrexate and intravenous immunoglobulin. A videofluoroscopic swallowing study revealed a large esophageal protrusion at the level of C5-C6, which was thought to be consistent with a cricopharyngeal bar, with large boluses unable to pass, leading to aspiration. After 10 weeks of treatment, the cricopharyngeal bar remained present, but swallowing had improved to the point that she was successfully swallowing all consistencies.

CONCLUSION

Dysphagia associated with IIM can be multifactorial, and can be due to the involvement of the muscles of swallowing in the inflammatory process, or due to restrictive pharyngeal defects, and determination of the cause of dysphagia can assist with management.