Idiopathic Inflammatory Myopathies
Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of disorders and commonly include dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Each one has different clinical features, histological findings and association
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11.1 Introduction The IIMs are diverse group of disorders having following common features. • • • • •
Onset is acute, subacute or chronic. Distribution is proximal and symmetrical (except IBM). Elevated CK (creatine kinase). EMG shows irritative muscle disease. Muscle biopsy reveals inflammatory exudates.
When inflammatory myopathies are associated with connective tissue disease like SLE or scleroderma, they are known as overlap syndrome (OS) (Dimachkie and Barohn 2012). Interstitial lung disease may be associated with juvenile dermatomyositis (JDM) along with Jo-1 antibodies (Hochberg et al. 1984; Van der Meulen et al. 2003; Marie et al. 2011). Malignancy are commonly seen with DM followed by PM and NM (Chen et al. 2010; Miller T et al. 2002; Miller J et al. 2002). Dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), necrotising myopathies (NM), eosinophilic, granulomatous and drug-induced myopathies are discussed in this chapter.
© Springer Nature Singapore Pte Ltd. 2018 S.V. Khadilkar et al., Neuromuscular Disorders, https://doi.org/10.1007/978-981-10-5361-0_11
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11 Idiopathic Inflammatory Myopathies
11.2 Epidemiology Incidence rates: 2–8 per million Prevalence rates: 10–63 per million Cronin and Plotz (1990), Oddis et al. (1990), Patrick et al. (1999)
11.3 Clinical Features The common clinical denominator is the rapidly evolving, symmetric, proximal muscle weakness often with dysphagia and neck weakness. Apart from this, some clinical clues exist in various forms of IIMs, which are tabulated below (Table 11.1). Table 11.1 Clinical features of various IIMs Diagnosis Dermatomyositis
Salient clinical features Age of onset: 10–40 years of age Disease onset: Acute or insidious Weakness: Proximal and painless Skin manifestations: Heliotrope rash, Gottron’s papules (Fig. 11.1), V-sign and Shawl sign (Quinter et al. 2012), subcutaneous calcification, pruritus (Schmeling et al. 2011; Shirani et al. 2004; Hundley et al. 2006; Medsger and Oddis 1995) Polyarthritis (Tymms and Webb 1985) Two types: 1. Isolated skin manifestation is known as amyopathic DM 2. Isolated muscle involvement is known as adermatopathic DM
Antisynthetase syndrome
Mechanic’s hands, arthritis, Raynaud’s phenomenon, interstitial lung disease Age of onset: Over 20 years of age Disease onset: Subacute or insidious Weakness: Proximal and symmetrical (Bohan and Peter 1975) Dysphagia (1/3rd patients), jaw-opening weakness in few patients (Pal and Sanyal 2011) Neck and shoulder weakness, finger extensor weakness, respiratory weakness (Khadilkar et al. 2014) Age of onset: After 50 years age Weakness: Distal and asymmetric – deltoids, quadriceps, forearm muscles, ankle dorsiflexors Course: Indolent and treatment refractory (Cohen et al. 1989) Additional neuropathy may occur (Leff et al. 1993) Onset: Subacute Clinical features: Progressive and proximal (Van der Meulen et al. 2003), myalgia, dysphagia Associations: Malignancy esp. adenocarcinoma Necrotizing myopathy with pipestem capillaries: Weakness, vascu
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