Key Clinical Points
Most myopathies tend to present with proximal (large) muscle group involvement.
Inclusion body myositis (IBM), a gradual and insidious loss of muscle mass and strength, is associated with characteristic histology and normal to mildly elevated muscle enzyme levels. It is the most common form of inflammatory myositis in older adults.
Older adults are at risk for multiple drug-induced myopathies, including those related to corticosteroids, heavy ethanol use, and lipid-lowering agents.
Healthy muscle contributes to metabolic processes and functional status in humans. Myopathies are not uncommon in older adults, and when present, magnify the effects of age-related decline in muscle structure, mass, and function. This chapter reviews the common myopathies seen in older people as well as polymyalgia rheumatica and giant cell arteritis. Please see Chapter 49 for age-related changes in muscle and sarcopenia.
CLINICAL EVALUATION OF MUSCLE DISEASE SYMPTOMS IN OLDER PEOPLE
The age-unrestricted list of conditions that can cause muscle disease symptoms is extensive. Candidate conditions are typically categorized as either acquired (autoimmune, endocrine disorder-related, toxin or drug-associated, amyloid, infectious, cancer-related, and others) or inherited (muscular dystrophies, metabolic myopathies, muscle channelopathies). The approach to the individual with myopathic symptoms is not age-specific, but the results must account for age-related variations within each component of the evaluation (see Figure 100-1). Most importantly, it is essential to factor in the coexistent medical conditions, impact on the activities of daily living (ADL) and instrumental activities of daily living (IADL), and the risks versus benefits of initiating the treatments for the underlying medical condition.
Approach to evaluation of myopathy in older adults.
As most extremity muscle bulk is proximal, symptoms of myopathic weakness tend to be associated with shoulder and hip girdle motions. Patients may report the inability to perform a specific task due to weakness or poor stamina in performing tasks once readily accomplished. Independence with ADLs, maintenance of balance and gait, and freedom from falling should be addressed as all are sustained in part by maintaining muscle strength. Muscle pain is an uncommon symptom of primary myopathy in older people. It can be seen in polymyalgia rheumatica (PMR) or a regional or generalized musculoskeletal disorder, such a rotator cuff tendinopathy, subacromial or trochanteric bursitis, or fibromyalgia syndrome.
Documenting the severity of initial and serial assessments of muscle strength should be based on the MRC grading scale of 0 to 5. The healthy older person should sustain muscle contraction against full resistance for 2 to 4 seconds, usually allotted to test ...