Neuronal-intermediate Filament Antibody Paraneoplastic Syndrome in a Patient with Merkel Cell Carcinoma: a Case Report
Neha Sehgal1, Oluwasegun Emenogu1, Stephen Lee1, Amy Espinal1, Adil Javed1
1University of Chicago Medical Center
Objective:
N/A
Background:
Neuronal intermediate filaments (NIF) are intermediate filaments which are found in the cytoplasm of axons and function as structures to increase the diameter of axons. Neuronal intermediate filament antibody-associated paraneoplastic syndrome has been associated with neuroendocrine malignancies. Here we present a case report of a patient with progressive neurologic symptoms found to have NIF-Ab positive paraneoplastic syndrome secondary to newly-diagnosed Merkel cell carcinoma.
Design/Methods:
N/A
Results:

A 73-year-old male presented to University of Chicago Medical Center with one week history of progressive weakness, dizziness, nausea and a fall. Neurological examination revealed sustained nystagmus in all directions, left tongue deviation, and severe dysarthria. MRI brain with and without contrast was unrevealing for acute intracranial abnormality. Whole-body PET scan revealed a hypermetabolic lesion in the left axilla which upon biopsy revealed Merkel cell carcinoma (MCC), T0N1bM0 Stage III indicating localized disease. He was empirically treated with IVIG and steroid taper for suspected paraneoplastic syndrome, then started on chemotherapy (etoposide + cisplatin) for MCC. He underwent L axillary lymph node resection. ICU course was complicated by profound respiratory failure preventing successful extubation.

Initial results from lumbar puncture revealed normal protein and glucose with elevated WBC to 23 with a lymphocytic predominance.  Further CSF analysis demonstrated positive NIF IFA Titer (1:512), positive alpha-internexin cell binding assay, positive NIF light chain and heavy chain CBA, which supports a diagnosis of paraneoplastic syndrome, specifically secondary to Merkel cell carcinoma as seen in this patient.
Conclusions:

Neuroendocrine tumors are associated with paraneoplastic syndromes. This case illustrates the specific antibodies associated with an aggressive paraneoplastic syndrome in a patient with MCC, even in localized disease.

10.1212/WNL.0000000000216158
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