Strategy for suspected myositis

Myositis Multidisciplinary Clinic in a Tertiary Referral Center

Background

Idiopathic inflammatory myopathies (IIM) are a rare heterogeneous group of diseases characterised by chronic skeletal muscle inflammation, but other organs are also frequently involved. IMM represent a diagnostic challenge and a multidisciplinary approach is important to ensure successful diagnosis and adequate follow-up of these patients.

Objective

To describe the general functioning of our multidisciplinary myositis clinic, highlighting the benefits of multidisciplinary team management in patients with confirmed or suspected IIM and to characterise our clinical experience.

Methods

Description of the organization of a dedicated multidisciplinary myositis outpatient clinic, supported by IMM specific electronic assessment tools and protocols based on our Portuguese Register - Reuma.pt. In addition, an overview of our activity between 2017 and 2022 is provided.

Results

An IIM multidisciplinary care clinic, based on a close collaboration between Rheumatologists, Dermatologists and Physiatrist is detailed in this paper. One hundred and eighty-five patients were assessed in our myositis clinic; 138 (75%) of those were female, with a median age of 58 [45-70] years. At the last appointment, 130 patients had a confirmed IIM diagnosis, and the mean disease duration was 4 [2-6] years. The most frequent diagnosis was dermatomyositis (n = 34, 26.2%), followed by antisynthetase syndrome (n = 27, 20.8%) and clinically amyopathic/paucimyopathic dermatomyositis (n = 18, 13.8%). Twenty-four patients (18.5%) were on monotherapy and 94 (72.3%) were on combination therapy.

Conclusion

A multidisciplinary approach is important to ensure the correct diagnosis and follow-up of these patients. A myositis clinic, with a standardised practice at a tertiary hospital level, contributes to a standardization of care and opens research opportunities.

[Myositis: From classification to diagnosis]

Idiopathic inflammatory myopathies, or IIM, are a group of acquired diseases that affect the muscle to a certain extent, and may also affect other organs. They include dermatomyositis, which can affect the muscle eventualy, with a typical skin rash; inclusion body myositis, with a purely muscular expression resulting in a slow progressive deficit; and the former group of "polymyositis", a misnomer that actually includes other categories of IIM, such as immune-mediated necrotizing myopathies, with a severe muscle involvement often presents from the onset of the disease; antisynthetase syndrome, which combines muscle damage, joint involvement and a potentially life-threatening lung disease; and overlapping myositis, which combines muscle damage with other organs involvement connected to another autoimmune disease. The diagnosis of IIM is based on rigorous clinical examination and interrogation, electromyographic data and immunological testing for myositis specific antibodies. This antibody dosage must be extended or repeated if necessary to classify correctly the muscle disease under investigation, as the available tests may not perform well enough. Muscle biopsy, although very informative, is not anymore systematically recommended when the clinic and the antibodies are typical. However, some forms of IIM are sometimes difficult to classify; in these cases, muscle biopsy plays a crucial role in the precise etiological diagnosis.