Immune myopathy with myocyte necrosis
Necrotizing Autoimmune Myopathy, Immune-mediated necrotizing myopathy, Anti-HMG-CoA myopathy, Anti-SRP myopathy, Autoimmune necrotizing myositis, IMNM, NAM
Type of disease: Rare Condition or Disease
Necrotizing autoimmune myopathy (NAM) is a rare form of idiopathic inflammatory myopathy characterized clinically by acute or subacute proximal muscle weakness, and histopathologically by myocyte necrosis and regeneration without significant inflammation.
The prevalence and annual incidence of NAM are not known but the disorder is very rare. About 300 cases have been reported to date.
Age of onset ranges from 30 to 70 years of age in reported cases. The main presenting feature of NAM is subacute severe symmetrical proximal myopathy, with a markedly elevated creatine kinase (CK) level. Its presentation is similar to that of polymyositis (see this term) with upper and lower limb weakness causing difficulty in moving from a sitting position, climbing stairs, or lifting objects The neck flexor, pharyngeal, and respiratorymuscles may also be involved. Other manifestations include fatigue, weight loss dysphagia and dyspnea. Interstitial lung disease (see this term) and cardiac involvement have also been reported. The course is often severe but may be self-limiting and recovery may occur within weeks to months of discontinuing the causative agent, if identified.