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Updated: Aug 2, 2026
Semi-automated Analysis of Mouse Skeletal Muscle Morphology and Fiber-type Composition
Published on: August 31, 2017
Quantitative morphometric study of muscle in inclusion body myositis
A Verma1, W G Bradley, N W Soule
1Department of Neurology, University of Vermont College of Medicine, Burlington.
Abstract:
Clinical and electromyographic findings do not clearly distinguish inclusion body myositis (IBM) from chronic polymyositis (PM). The rimmed vacuoles and filamentous nuclear and cytoplasmic inclusions that characterize IBM are often sparse and may be overlooked; conversely, these features may occasionally be seen in other diseases. Preliminary studies suggested that muscle fiber hypertrophy occurred more frequently in IBM than in PM. To investigate whether fiber hypertrophy can be used to improve the ability to separate IBM from PM, we report a morphometric analysis of 28 IBM cases, 22 PM and 22 dermatomyositis (DM) cases. The analysis, using a computer automated system, included proportion of hypertrophied fibers and also fiber type proportions, average fiber diameter, proportion of atrophic and angulated fibers, and the co-dispersion index (CDI). The proportion of hypertrophied fibers was greater in IBM than the other two conditions (IBM (mean +/- SEM) 31.0 +/- 4.7% and 12.2 +/- 2.4% for type 1 and type 2 fibers, respectively, compared to 9.8 +/- 3.0% and 3.3 +/- 1.7% in PM, and 7.7 +/- 2.7% and 3.9 +/- 1.9% in DM). These differences were statistically significant (P < 0.05) in both sexes for type 1 fibers and in women for type 2 fibers. Also, the average fiber size and hypertrophy factors for type 1 and type 2 fibers were increased in IBM compared to PM and DM. This study confirms that the presence of muscle fiber hypertrophy in biopsies from IBM patients may help differentiate them from other clinically similar inflammatory myopathies.
Insights
Muscle fiber hypertrophy is more common in inclusion body myositis (IBM) than in polymyositis (PM) or dermatomyositis (DM). This finding aids in distinguishing IBM from other inflammatory myopathies.
Area of Science:
- Neurology
- Pathology
- Biomedical Engineering
Background:
- Distinguishing inclusion body myositis (IBM) from polymyositis (PM) and dermatomyositis (DM) is challenging due to overlapping clinical and electromyographic findings.
- Characteristic IBM features like rimmed vacuoles and inclusions can be sparse or present in other myopathies, complicating diagnosis.
- Previous research suggested increased muscle fiber hypertrophy in IBM compared to PM.
Purpose of the Study:
- To investigate if muscle fiber hypertrophy can improve the diagnostic differentiation between IBM and other inflammatory myopathies (PM, DM).
- To quantitatively assess muscle fiber characteristics in IBM, PM, and DM using morphometric analysis.
Main Methods:
- A morphometric analysis was performed on muscle biopsy samples from 28 IBM, 22 PM, and 22 DM cases.
- A computer-automated system was used to analyze the proportion of hypertrophied fibers, fiber type proportions, average fiber diameter, proportion of atrophic/angulated fibers, and co-dispersion index (CDI).
Main Results:
- The proportion of hypertrophied fibers was significantly greater in IBM (31.0% type 1, 12.2% type 2) compared to PM (9.8% type 1, 3.3% type 2) and DM (7.7% type 1, 3.9% type 2) (P < 0.05).
- Statistically significant differences in hypertrophied type 1 fibers were observed in both sexes, and in type 2 fibers in women.
- IBM cases showed increased average fiber size and hypertrophy factors for both fiber types compared to PM and DM.
Conclusions:
- Muscle fiber hypertrophy is a significant feature that can aid in differentiating inclusion body myositis from polymyositis and dermatomyositis.
- Quantitative morphometric analysis of muscle biopsies provides valuable insights for diagnosing inflammatory myopathies.
