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14 | InTouch WINTER 2024 Inclusion body myositis (IBM) is an inflammatory muscle disease, characterized by chronic inflammation and slowly progressive muscle weakness of both distal (further from torso) and proximal (closer to torso) muscles. Inclusion body myositis (IBM) is an inflammatory muscle disease, characterized by chronic inflammation and slowly progressive muscle weakness of both distal (further from torso) and proximal (closer to torso) muscles. It is the most common age- related muscle disease, with cases typically occurring in people over 50 years old, though symptoms can begin at any age between 30 and 80 years. The prevalence of IBM in the general population is between 2 and 7 per 100,000 people. However, among individuals over the age of 50, the prevalence increases to approximately 18 per 100,000 people. IBM affects about 2 to 3 times more males than females. Inclusion body myositis is one of a group of rare disorders called idiopathic inflammatory myopathies. This group includes dermatomyositis, polymyositis, and necrotizing myopathy, which are all conditions supported by the MDA. The term“idiopathic” is used to describe a condition or disease that arises spontaneously or for which the cause is unknown. IBM can be considered idiopathic because its exact cause or trigger is not fully understood. However, it is believed that a particular person’s genetic makeup and immune systemmight make themmore susceptible to IBM than the general population. Inclusion body myositis is named for a distinctive feature observed in muscle tissue under a microscope. In Inclusion Body Myositis YOUR CONDITION IN REVIEW IBM, certain proteins that are normally processed and broken down in muscle cells start to accumulate abnormally. These proteins clump together to form“inclusion bodies”which can be seen inside the muscle cells. IBM is sometimes abbreviated sIBM for “sporadic” inclusion body myositis. You may also hear the term familial inclusion body myositis (fIBM) in the rare instance where two members of the same family have IBM. This is not to be confused with hereditary inclusion body myopathy (HIBM) which has a different pattern of onset and weakness, can be clearly linked to a genetic cause, and is not considered an inflammatory muscle disease. Features of IBM Despite evidence of inflammation in the muscles, IBM is typically painless and develops gradually, often going unnoticed in the early stages. Difficulty with stairs or standing up from a low chair are common early signs of IBM due to weakness of the thigh muscles. Some may initially notice weakness of hand grip and difficulty grasping, pinching, buttoning, manipulating keys, and other fine motor tasks. Weakness of the muscles that dorsiflex the ankle (i.e., pick up the foot) can result in tripping and falling. Asymmetry of muscle weakness (affecting one side Some may initially notice weakness of hand grip and difficulty grasping, pinching, buttoning, manipulating keys, and other fine motor tasks.