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Concurrent Sporadic Late‐Onset Nemaline Myopathy and an Excessive Glycogen Accumulation Associated With Monoclonal Gammopathy.

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Title: Concurrent Sporadic Late‐Onset Nemaline Myopathy and an Excessive Glycogen Accumulation Associated With Monoclonal Gammopathy.
Authors: Jones, Felipe J. S. (AUTHOR), Cheema, Ikreet (AUTHOR), Laughlin, Ruple S. (AUTHOR), Muchtar, Eli (AUTHOR), Liewluck, Teerin (AUTHOR)
Source: European Journal of Neurology. Mar2026, Vol. 33 Issue 3, p1-3. 3p.
Subjects: Nemaline myopathy, Glycogen, Muscle diseases, Stem cell transplantation, Monoclonal gammopathies, Immunotherapy
Abstract: Background: Monoclonal gammopathy‐associated myopathies (MGAMs) include light chain (AL) amyloid myopathy, sporadic late‐onset nemaline myopathy (SLONM), and vacuolar myopathy with monoclonal gammopathy and stiffness (VAMMGAS). These subtypes usually occur separately, although rare overlap has been described. We report a patient with monoclonal gammopathy and concurrent SLONM and excessive glycogen accumulation, resembling VAMMGAS but with distinct features. Methods: Case report with clinical, electrophysiological, pathological, and therapeutic characterization of a patient with IgG‐kappa monoclonal gammopathy and coexisting SLONM and glycogen accumulation within muscle fibers. Results: A 69‐year‐old man developed subacute progressive axial and limb weakness, head drop, dysphagia, and weight loss. Examination showed proximal/distal weakness, neck extensor weakness, and lumbar hyperlordosis. EMG revealed myopathic motor unit potentials without electrical myotonia or complex repetitive discharges. Serum studies identified IgG‐kappa monoclonal protein with elevated kappa light chain and ratio. Muscle biopsy demonstrated nemaline rods (1% of fibers) and scattered fibers with non‐rimmed vacuoles (0.3% of fibers) containing PAS‐positive, diastase‐labile material consistent with concurrent SLONM and glycogen storage myopathy‐like pathology. Genetic testing for congenital nemaline and glycogen storage myopathies was negative. Plasma‐cell directed therapy with daratumumab, lenalidomide, and dexamethasone led to rapid functional improvement and M‐protein reduction. Further gains followed autologous stem cell transplantation. Conclusion: This case expands the MGAM spectrum, highlighting co‐occurrence of SLONM and an excessive glycogen accumulation responsive to immunotherapy and transplantation. These findings suggest a spectrum of related disease processes. Recognition of this combined pathology is clinically important, as affected patients may benefit from targeted immunotherapy or stem cell transplantation. [ABSTRACT FROM AUTHOR]
Copyright of European Journal of Neurology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Psychology and Behavioral Sciences Collection
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  Label: Title
  Group: Ti
  Data: Concurrent Sporadic Late‐Onset Nemaline Myopathy and an Excessive Glycogen Accumulation Associated With Monoclonal Gammopathy.
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  Data: <searchLink fieldCode="AR" term="%22Jones%2C+Felipe+J%2E+S%2E%22">Jones, Felipe J. S.</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Cheema%2C+Ikreet%22">Cheema, Ikreet</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Laughlin%2C+Ruple+S%2E%22">Laughlin, Ruple S.</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Muchtar%2C+Eli%22">Muchtar, Eli</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Liewluck%2C+Teerin%22">Liewluck, Teerin</searchLink> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22European+Journal+of+Neurology%22">European Journal of Neurology</searchLink>. Mar2026, Vol. 33 Issue 3, p1-3. 3p.
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  Data: <searchLink fieldCode="DE" term="%22Nemaline+myopathy%22">Nemaline myopathy</searchLink><br /><searchLink fieldCode="DE" term="%22Glycogen%22">Glycogen</searchLink><br /><searchLink fieldCode="DE" term="%22Muscle+diseases%22">Muscle diseases</searchLink><br /><searchLink fieldCode="DE" term="%22Stem+cell+transplantation%22">Stem cell transplantation</searchLink><br /><searchLink fieldCode="DE" term="%22Monoclonal+gammopathies%22">Monoclonal gammopathies</searchLink><br /><searchLink fieldCode="DE" term="%22Immunotherapy%22">Immunotherapy</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Background: Monoclonal gammopathy‐associated myopathies (MGAMs) include light chain (AL) amyloid myopathy, sporadic late‐onset nemaline myopathy (SLONM), and vacuolar myopathy with monoclonal gammopathy and stiffness (VAMMGAS). These subtypes usually occur separately, although rare overlap has been described. We report a patient with monoclonal gammopathy and concurrent SLONM and excessive glycogen accumulation, resembling VAMMGAS but with distinct features. Methods: Case report with clinical, electrophysiological, pathological, and therapeutic characterization of a patient with IgG‐kappa monoclonal gammopathy and coexisting SLONM and glycogen accumulation within muscle fibers. Results: A 69‐year‐old man developed subacute progressive axial and limb weakness, head drop, dysphagia, and weight loss. Examination showed proximal/distal weakness, neck extensor weakness, and lumbar hyperlordosis. EMG revealed myopathic motor unit potentials without electrical myotonia or complex repetitive discharges. Serum studies identified IgG‐kappa monoclonal protein with elevated kappa light chain and ratio. Muscle biopsy demonstrated nemaline rods (1% of fibers) and scattered fibers with non‐rimmed vacuoles (0.3% of fibers) containing PAS‐positive, diastase‐labile material consistent with concurrent SLONM and glycogen storage myopathy‐like pathology. Genetic testing for congenital nemaline and glycogen storage myopathies was negative. Plasma‐cell directed therapy with daratumumab, lenalidomide, and dexamethasone led to rapid functional improvement and M‐protein reduction. Further gains followed autologous stem cell transplantation. Conclusion: This case expands the MGAM spectrum, highlighting co‐occurrence of SLONM and an excessive glycogen accumulation responsive to immunotherapy and transplantation. These findings suggest a spectrum of related disease processes. Recognition of this combined pathology is clinically important, as affected patients may benefit from targeted immunotherapy or stem cell transplantation. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of European Journal of Neurology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1111/ene.70557
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        Text: English
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      – SubjectFull: Nemaline myopathy
        Type: general
      – SubjectFull: Glycogen
        Type: general
      – SubjectFull: Muscle diseases
        Type: general
      – SubjectFull: Stem cell transplantation
        Type: general
      – SubjectFull: Monoclonal gammopathies
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      – SubjectFull: Immunotherapy
        Type: general
    Titles:
      – TitleFull: Concurrent Sporadic Late‐Onset Nemaline Myopathy and an Excessive Glycogen Accumulation Associated With Monoclonal Gammopathy.
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            NameFull: Jones, Felipe J. S.
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            NameFull: Cheema, Ikreet
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              Text: Mar2026
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              Y: 2026
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