Myositis - General Overview Flashcards
What are some investigations you can do to work-up a patient with suspected myositis?
What are the clinically differentiating features between the idiopathic inflammatory myopathies (IIM)?
Patients with polymyositis (PM), dermatomyositis (DM) and necrotising myopathy will typically develop symmetrical and proximal muscle weakness over a period of weeks to few months. Patients with inclusion body myositis (IBM) are typically older than the PM/DM patients (mean age at onset 65-70 years) and will often have a slowly progressive weakness that may be asymmetric at least initially and affects also distal muscle groups. In addition, their creatinine kinase (CK) values are usually lower than the values in patients with PM, DM or necrotising myopathy.
Proximal oesophageal affection does not clinically distinguish between the IIMs. By performing dynamic x-ray barium swallow study patients with IBM, in contrast to patients with the other IIMs, often have cricopharyngeal dysfunction or spasm.
What are the 8 conditions that encompass the clinical spectrum of idiopathic inflammatory myopathy (IIM)?
- Dermatomyositis (DM)
- Polymyositis (PM)
- Juvenile dermatomyositis (JDM)
- Necrotising myopathy
- Inclusion body myositis (IBM)
- Amyopathic / hypomyopathic dermatomyositis
- Myositis in overlap syndromes
- Paraneoplastic myopathy
What is the relative risk of cancer in dermatomyositis?
Adult-onset dermatomyositis carries an increased risk of malignancy, but this is not the case in juvenile onset dermatomyositis. Increased risk has been confirmed in several population-based studies, with standardized incidence ratios of cancer ranging from 2.0 to 6.0. The association between cancer and inflammatory myopathies has been extensively reported in dermatomyositis (DM), but to a lesser degree in polymyositis (PM). Inclusion body myositis (IBM) has shown conflicting results regarding the cancer risk. The patients are generally older and recent studies have not confirmed an increased risk of cancer compared to age matched background population. Amyopathic dermatomyositis is reported to have a similar risk as DM and necrotizing myopathy is also reported to be associated with cancer.
What cancers are commonly associated with DM in
a) Western countries?
b) Southeast Asia?
In Western countries, common malignancies associated with DM include:
1) ovarian
2) lung
3) pancreatic
4) gastric and;
5) colorectal cancers
(according to IMACS, lymphoma and breast cancers are also among the most common forms of cancers associated with IIM)
Among patients in Southeast Asia, DM is seen strongly associated with nasopharyngeal carcinoma.
In patients with DM, when does cancer usually present compared to the time of diagnosis? What percentage of people are diagnosed with cancer in the immediate years following IIM diagnosis?
Cancer is most commonly recognized within 2 years of the diagnosis (according to the EULAR 19th Course in Rheumatology Module).
According to IMACS (International Myositis Assessment and Clinical Studies) group, adult-onset IIM is associated with an increased risk of cancer, particularly within the 3 years prior to and the 3 years after IIM onset. Evidence suggests that up to one in four people with IIM are diagnosed with cancer within 3 years of IIM onset.
In patients with DM, what are additional risk factors for underlying malignancy?
- Older age of onset
- Resistance to treatment
- Severe cutaneous involvement with ulcerations
- Leukocytoclastic vasculitis
- Severe and therapy resistant muscle disease
- Paraneoplastic myopathy has been associated with anti-NXP-2 (anti-p140) and anti-TIF1γ (anti-p155, anti-p155/140) antibodies.
Screening for underlying malignancy in patients with dermatomyositis is mandatory in patients of what age?
Screening for underlying malignancy is mandatory in patients above the age of 40. with a new diagnosis of inflammatory myositis. Currently, there is no consensus on how extensive such screening work-up should be. A careful history, a complete physical examination, appropriate laboratory tests, and age-appropriate cancer screening are indicated. Any abnormalities detected that may signal the presence of occult cancer should be further investigated.
Is there an increased risk of cancer in patients with inclusion-body myositis?
Existing evidence indicates that inclusion body myositis (IBM)
is not associated with an increased risk of cancer. In particular,
a nationwide Norwegian-based cohort study by Dobloug et al. cal
culated a cancer standardized incidence rate of 1.0 (95% CI 0.6–2.1)
in 100 cases of IBM, indicating a cancer risk similar to that of the
general population. However, emerging evidence suggests a poten
tial association between IBM and T cell large granular lymphocytic
leukaemia; ongoing research could further delineate this association
and potentially inform the need for screening
According to the International Myositis Assessment and Clinical Studies Group (IMACS) what are ‘High-Risk’ features for cancer in IIM?
According to the International Myositis Assessment and Clinical Studies (IMACS) Group, what are ‘Intermediate Risk’ features for cancer in IIM?
According to the International Myositis Assessment and Clinical Studies (IMACS) Group, what are ‘Low-Risk’ features in IIM?
