Inclusion body myositis
Inclusion body myositis (IBM) is an inflammatory muscle disorder with insidious onset of leg weakness and elevated serum CK. Treatment aims to optimize muscle strength and includes physical therapy, assistive devices, and immunosuppressive medications, particularly for those with associated autoimmune conditions or rapidly progressing weakness. Immune globulin and oxandrolone have unclear benefits and are not recommended.
Inclusion Body Myositis (IBM): Overview and Classification
Inclusion body myositis (IBM) is classified along with polymyositis, dermatomyositis and autoimmune necrotizing myopathy as one of the idiopathic inflammatory myopathies. Patients with IBM usually present with the insidious onset (over an average 5 years) of asymmetrical proximal leg weakness with mild elevation of serum CK. IBM is associated with some autoimmune diseases, such as, Sjögren's syndrome, sarcoidosis, or T cell large granular lymphocytic leukemia. (1, 2)
Primary Treatment Goals in IBM
The primary goal of therapy in IBM is to optimise muscle strength and function. Treatment includes non- pharmacological measures and immunosuppressive agents. Given the slowly progressive and variable course of the disease, it can be quite challenging to determine if disease modifying agents lead to an objective improvement of muscle strength. (3)
Non-Pharmacological Measures in IBM Management
Non- pharmacological measures include physical therapy, such as, aerobic, functional muscle strengthening program, assistive devices, such as, a cane, walker, ankle foot orthoses and occupational therapy (splints, adaptive equipment, grip strengthening devices). Also, patients with dysphagia should be evaluated by a speech therapist. (4, 5)
Immunosuppressive Medications in IBM
Immunosuppressive medications are required for some patients who have IBM and Sjögren's syndrome, those with rapidly progressive proximal limb weakness, or markedly elevated creatine kinase, then. They include glucocorticoids (prednisolone 1mg/kg daily for about two to three months). If steroids improve the power, then, other agent is added including methotrexate (starting at 10 mg/week) or azathioprine (1.5- 2.5 mg/kg per day) for a trial period of three to six months and slowly taper prednisolone doses. If steroids fail to improve the power, then, methotrexate or azathioprine is considered. (5, 6)
Other Agents and Their Consideration
Other agents, such as, IV immune globulin (IVIG), or oxandrolone are tried in IBM without clear benefit and are not recommended. (7)
References
1- Needham M, James I, Corbett A, Day T, Christiansen F, Phillips B, et al. Sporadic inclusion body myositis: phenotypic variability and influence of HLA-DR3 in a cohort of 57 Australian cases. Journal of neurology, neurosurgery, and psychiatry. 2008 Sep; 79(9):1056–1060.
2-Benveniste O, Guiguet M, Freebody J, Dubourg O, Squier W, Maisonobe T, et al. Long-term observational study of sporadic inclusion body myositis. Brain. 2011 Nov; 134(Pt 11):3176–3184.
3-Dalakas MC. Sporadic inclusion body myositis--diagnosis, pathogenesis and therapeutic strategies. Nature clinical practice Neurology. 2006 Aug; 2(8):437–447.
4-Waclawik AJ, Rao VK. Effective treatment of severe finger flexion weakness in inclusion body myositis using tendon transfers. J Clin Neuromuscul Dis 2002; 4:31.
5-Breithaupt M, Schmidt J. Update on treatment of inclusion body myositis.Current rheumatology reports. 2013 May.15(5):329.
6-Lloyd TE. Novel therapeutic approaches for inclusion body myositis.Current opinion in rheumatology. 2010 Nov; 22(6):658–664.
7-Rutkove SB, Parker RA, Nardin RA, et al. A pilot randomized trial of oxandrolone in inclusion body myositis. Neurology 2002; 58:1081.
