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Intranuclear rod myopathy, a rare and morphologically striking variant of nemaline rod myopathy
Douglas A Weeks1, Randal R Nixon, Vassil Kaimaktchiev
1Department of Pathology, Oregon Health and Science University, Portland, Oregon 97239, USA. weeksd@ohsu.edu
Abstract:
A 4-year-old boy with muscle weakness underwent skeletal muscle biopsies. Light microscopy showed distinct eosinophilic inclusions within the majority of muscle cell nuclei, but none in the cytoplasm. Electron microscopy revealed crystalline, round to rod-shaped inclusions in the muscle cell nuclei. The inclusions stained positively for alpha-actinin. Intranuclear inclusions identical to those seen here have been described in rare cases of nemaline rod myopathy, though almost always together with classic intracytoplasmic rods. This case illustrates the importance of electron microscopy in the diagnosis of rare myopathies and in the characterization of cellular inclusions of unknown origin.
Insights
This study details a rare case of nemaline rod myopathy with intranuclear inclusions. Electron microscopy was crucial for diagnosing this muscle weakness in a young boy.
Area of Science:
- Neurology
- Pathology
- Genetics
Background:
- Nemaline rod myopathy is a rare neuromuscular disorder characterized by muscle weakness.
- Classic nemaline myopathy typically presents with intracytoplasmic inclusions called nemaline rods.
Observation:
- A 4-year-old boy presented with muscle weakness and underwent skeletal muscle biopsy.
- Light microscopy revealed eosinophilic inclusions within muscle cell nuclei.
- Electron microscopy identified crystalline, round to rod-shaped intranuclear inclusions positive for alpha-actinin.
Findings:
- The patient exhibited exclusively intranuclear inclusions, unlike typical cases of nemaline rod myopathy.
- These intranuclear inclusions, positive for alpha-actinin, are a rare finding in neuromuscular disorders.
- The case highlights a variant presentation of nemaline rod myopathy.
Implications:
- Electron microscopy is essential for diagnosing rare myopathies and characterizing unusual cellular inclusions.
- This finding expands the spectrum of nemaline rod myopathy presentations.
- Further research into the pathogenesis of intranuclear inclusions is warranted.