Myositis Mimics

Abstract

Patients with autoimmune myositis typically present with muscle weakness, elevated serum levels of muscle enzymes, and abnormal muscle biopsies. However, patients with other acquired myopathies or genetic muscle diseases may have remarkably similar presentations. Making the correct diagnosis of another muscle disease can prevent these patients from being exposed to the risks of immunosuppressive medications, which benefit those with myositis, but not those with other types of muscle disease. Here, we review some of the most common acquired and inherited muscle diseases that can mimic autoimmune myositis, including inclusion body myositis, limb girdle muscular dystrophies, metabolic myopathies, mitochondrial myopathies, and endocrine myopathies. We emphasize aspects of the medical history, physical exam, laboratory evaluation, and muscle biopsy analysis that can help clinicians distinguish myositis mimics from true autoimmune myositis.

SAT0625 Ultrasound assessment of joints and enthesis in a cohort of patients affected by ochronosis: how common is inflammation?

“…The results of this US study showed that joint inflammation is common in ochronotic patients, associated in some cases with peripheral enthesis involvement confirming previously published data (1). The prevalence and the characteristics of the inflammatory manifestations should be further studied in larger cohorts of patients as they could play an important role in the joint damage process in these patients and provide a rationale for the use of new drugs.…”

“…In 4 patients, the histological features did not present specific characteristics of a myopathy, but revealed a preferential atrophy of type 2 fibbers, usually associated with prolonged corticosteroid therapy. Among the others, 9 (19.6%) were compatible with inflammatory myopathies, namely polymyositis (6), dermatomyositis (1), inclusion body myopathy (1), and localized nodular myositis (1). In the latter case, the patient had a different clinical presentation, with intermittent episodes of pain, oedema and flushing of different muscle groups.…”

“…Background: Bone damage in rheumatoid arthritis (RA) typically emerges at certain anatomical hotspots corresponding to the so-called "bare area", an intra-articular region between the cartilage and the insertion site of the joint capsule (1,2). We hypothesized that this region exhibits certain micro-anatomical properties, which facilitates the emergence of bone erosions.…”

A review of inflammatory idiopathic myopathy focusing on polymyositis

“…Muscular dystrophy is a group of progressive myopathic disorders caused by genetic defects. Although biopsies taken from these patients may initially show endomysial inflammatory cell infiltrate, this tends to be limited to areas adjacent to necrotic muscle fibres, unlike PM .…”

Use of magnetic resonance imaging in the diagnosis of idiopathic inflammatory myopathies

“…Наиболее сложным может быть дифференциальный диагноз между ПМ, СМВ и заболеваниями группы поясно-конечностных мышечных дистрофий (ПКМД) с поздним дебютом. Так, у пациентов с ИВМ и ПКМД отмечается прогрессирующая мышечная слабость, повышен уровень мышечных ферментов, миографическая картина характеризуется первично-мышечным уровнем поражения, а при световой микроскопии могут выявляться признаки мышечного воспаления [3].…”