Objective: Describe an unusual presentation of leg posturing and dystonic features in a patient with diagnosis of atypical parkinsonism, which was ultimately found to be related to a sacral mass.

Background: A 59 year old man with history of elevated WBC count presented for diagnosis of degenerative parkinsonism, possibly atypical parkinsonism, after developing right foot posturing 2 years previous. The foot intially started inverting, with more fixed posture, lack of action inducement or sensory trick, contracture, and association with pain and discomfort in the foot that led to being wheelchair dependent one year after onset. On presentation to movement disorders specialist, he was noted to have mild right sided arm rest tremor, rigidity, and bradykinesia which was not previously recognized. MRI brain and enre spine and extensive lab workup did not reveal any secondary causes and diagnosis of atypical parkinsonism was suspected. Treatment trials of baclofen, botulinum toxin, levodopa, and neuropathic pain agents were unsuccessful.

Method: Case report and literature review

Results: Progressive leg pain and weakness prompted repeat of EMG 2 years after initial normal EMG, which showed electrophysiological evidence of an active right sided lumbosacral radioculoplexopathy affecting L4-S2 levels. Focused MRI of the sacral region/lumbar plexus revealed previously unseen large 12cm tissue mass with deep pelvic and superficial subcutaneous involvement, displacing the lumbar plexus. Biopsy showed transformed/transforming splenic marginal zone lymphoma (likely large B-cell lymphoma) and R-CHOP chemotherapy regimen was initiated with metabolic resolution of tumor to date but no relief from disability and neurological morbidity.

Conclusion: Consideration should be taken to consider alternate diagnosis for painful atypical leg dystonia, even in cases that appear to be otherwise fairly consistent with presentation of atypical parkinsonism. Very few case reports exist of misdiagnosis of lymphoma mimicking other syndromes, reported to include inflammatory myelopathy, inflammatory lumbosacral plexopathy, atypical parkinsonism, and demyelinating disease of the CNS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/sacral-mass-lesion-mimicking-atypical-foot-dystonia-in-parkinsonian-pa0tient/