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Sporadic late onset nemaline myopathy
Nizar Chahin1, Duygu Selcen, Andrew G Engel
1Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA.
Neurology
|September 9, 2005
Summary
Sporadic late-onset nemaline myopathy (SLONM) presents with subacute weakness and normal CK levels. Associated monoclonal gammopathy indicates a poor prognosis, while immunotherapy offers uncertain benefits.
Area of Science:
- Neurology
- Muscle Diseases
Background:
- Sporadic late-onset nemaline myopathy (SLONM) is an uncommon neuromuscular disorder with an unknown cause.
- This review focuses on non-HIV-related cases.
Purpose of the Study:
- To delineate the clinicopathologic characteristics and patient outcomes of sporadic late-onset nemaline myopathy (SLONM).
Main Methods:
- Analysis of clinical data, electromyography (EMG), histochemistry, immunocytochemistry, and electron microscopy.
- Long-term follow-up of 14 patients diagnosed with SLONM between 1975 and 2003.
- Evaluation of diagnostic confirmation through specific staining techniques for nemaline structures.
Main Results:
- SLONM manifested between ages 43-81 with subacute onset, predominantly proximal weakness, and dysphagia in some patients.
- EMG revealed myopathic features with fibrillations, while serum creatine kinase (CK) levels remained normal or low.
- Monoclonal gammopathy was present in seven patients, correlating with a higher mortality rate due to respiratory failure, whereas patients without it had better survival.
- Histological examination confirmed nemaline rods, with electron microscopy identifying additional structural abnormalities.
Conclusions:
- Key diagnostic indicators for SLONM include subacute weakness after age 40, normal/low CK levels, myopathic EMG with fibrillations, and often monoclonal gammopathy.
- Confirmation relies on visualizing nemaline rods via trichrome or immunostained cryosections.
- The presence of monoclonal gammopathy signifies a poor prognosis in SLONM patients.