Inclusion body myositis: old and new concepts

Abstract

Inclusion body myositis (IBM) is the most common idiopathic inflammatory myopathy occurring in patients over the age of 50 years and probably accounts for about 30% of all inflammatory myopathies. Muscle biopsy characteristically reveals endomysial inflammation, small groups of atrophic fibres, eosinophilic cytoplasmic inclusions and muscle fibres with one or more rimmed vacuoles. However, any given biopsy may lack these histopathological abnormalities; the clinical examination is often the key to diagnosis. Early and often asymmetrical weakness and atrophy of the quadriceps and flexor forearm muscles (ie, wrist and finger flexors) are the clinical hallmarks of IBM. The pathogenesis of IBM is unknown. It may be autoimmune inflammatory myopathy or a primary degenerative myopathy with a secondary inflammatory. A prevailing theory is that there is an overproduction of beta-amyloid precursor protein in muscle fibres that is somehow cleaved into abnormal beta-amyloid, and the accumulation of the latter is somehow toxic to muscle fibres. However, there are many problems with this theory and more work needs to be done. Unfortunately, IBM is generally refractory to therapy. Further research into the pathogenesis, along with both preliminary small pilot trials and larger double blind, placebo controlled efficacy trials, are needed to make progress in our understanding and therapeutic approach for this disorder.

Polymyositis/Dermatomiositis: Differential Diagnosis

“…Спорадический миозит с включениями является уникальным сочетанием аутоиммунного воспаления с дегенеративными изменени-ями. Выявляются вакуолизация и депозиты амилоида в мышечных волокнах [9,10].…”

Diagnosis and treatment of the idiopathic inflammatory myopathies

“…Regarding resistant IBM disease, only small retrospective studies have demonstrated mild response to prednisone and response was not based on any objective improvement in muscle strength [Amato and Barohn, 2009]. …”

Multicenter questionnaire survey for sporadic inclusion body myositis in Japan

“…Sporadic inclusion body myositis (sIBM) is the most common form of inflammatory myopathy in those over the age of 50 years in Western countries [1][2][3]. Muscle weakness and atrophy in the quadriceps, wrist flexor, and finger flexors are typical neurological findings of sIBM.…”