Polymyositis masquerading as motor neuron disease.
BACKGROUND
Several conditions have been reported to mimic motor neuron disease (MND), and misdiagnosis remains a common clinical problem.


OBJECTIVE
To report a case of bulbar-onset polymyositis where the initial clinical presentation was suggestive of MND.


METHODS
A 73-year-old woman was admitted for investigation of acute-onset dysphagia without dysarthria. Examination revealed nasal dysphonia and severe oropharyngeal weakness. Subtle upper-limb weakness, brisk tendon reflexes, and fasciculations in the right deltoid muscle were also demonstrated. A clinical diagnosis of MND was entertained. The serum creatine kinase value was within the reference range. Findings from electromyographic studies, however, were suggestive of a myopathic rather than a neurodegenerative process, and a muscle biopsy specimen was diagnostic of polymyositis. The dysphagia rapidly resolved upon treatment with corticosteroids and azathioprine.


CONCLUSIONS
Bulbar-onset polymyositis may mimic MND, particularly in the absence of inflammatory markers or elevated muscle enzyme levels. Caution should be exercised in the clinical diagnosis of bulbar dysfunction, and further investigations such as electromyography and muscle biopsy are indicated to confirm the diagnosis.
Ryan
Aisling
A
Department of Neurology, National Institute for Neurology and Neurosurgery, Beaumont Hospital, Dublin, Ireland.
Nor
Azli M
AM
Costigan
Donal
D
Foley-Nolan
Daragh
D
El-Rafie
Ahmed
A
Farrell
Michael A
MA
Hardiman
Orla
O
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000368:Aged; D001379:Azathioprine / Q000627:therapeutic use; D001706:Biopsy; D002574:Cervical Vertebrae; D003680:Deglutition Disorders / Q000209:etiology*; D003937:Diagnosis, Differential; D004576:Electromyography; D005260:Female; D005774:Gastrostomy; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D016472:Motor Neuron Disease / Q000473:pathology*; D018482:Muscle, Skeletal / Q000473:pathology; D017285:Polymyositis / Q000150:complications / Q000473:pathology* / Q000503:physiopathology* / Q000628:therapy; D013128:Spinal Osteophytosis / Q000150:complications; D014832:Voice Disorders / Q000209:etiology
D000305:Adrenal Cortex Hormones; D007166:Immunosuppressive Agents; D001379:Azathioprine