What is the mortality and morbidity associated with sporadic inclusion body myositis (s-IBM)?

Updated: Jun 08, 2018
  • Author: Michael P Collins, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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The slow, relentless progression of muscle weakness in s-IBM leads to difficulty with ambulation, frequent falls, and eventual need for assistive-gait devices. Bone fractures and other complications may occur as a result of falls. Patients are often significantly disabled because of finger flexor weakness.

In a study of gait in 42 persons with s-IBM, muscle force values were found to be significantly lower than predicted values (P< .001). During habitual walking, gait speed and cadence were ≤83% of normal values. During fast walking, total gait cycle time was 133% of normal, while gait speed and cadence were 58% and 78%, respectively, of normal. [66]

Dysphagia due to weakness of the cricopharyngeal musculature may predispose individuals to aspiration pneumonia.

Mortality rate is difficult to assess based on current data. Affected individuals tend to be older, the disease is insidious and chronic, and patients often die of other medical problems. In a population-based study, the mean age of death of patients with s-IBM was not significantly different from that of the general population. Cause of death was disease-related (aspiration pneumonia and respiratory insufficiency) in 2 of 22 reported deaths. [64] In a 12-year follow-up study in the Netherlands, life expectancy was normal (81 years), although activities of daily living were restricted. [67] The most common cause of death was respiratory system disorders.

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