Charles Giuliani1, Abhigyan Datta1, Elizabeth Troy1, Georgios Manousakis1
1University of Minnesota
Background:
Anti-MAG neuropathy typically presents as a slowly progressive ataxic distal neuropathy. Occasionally, patients with MAG-antibodies may show clinical features and treatment responses more consistent with classic CIDP. We present a case of severe CIDP-MAG, initially misdiagnosed as ALS.
Results:
A 57 year-old male with a history of lymphoplasmacytic lymphoma with MYD9 L265 mutation, presented to our clinic with severe proximal greater than distal weakness (quadriparesis with MRC scores of 0-1 in proximal and 2-3 in distal musculature), and complete areflexia over the prior 15 months. Previous testing showed IgM Kappa monoclonal gammopathy and MAG IgM antibody titer of 1:70,000. Serum paraneoplastic and paranodopathy-related antibodies, VEGF, and fat aspirate for amyloid were negative. CSF showed protein of 79 mg/dl without pleocytosis. He was treated with Bendamustine and Rituximab without benefit; subsequently, another tertiary center diagnosed him with motor neuron disease superimposed on coincidental paraproteinemic sensorimotor neuropathy. Review of previous EMG studies showed widespread denervation changes, but also a generalized demyelinating polyneuropathy with low median and ulnar nerve terminal latency indices. Sural nerve biopsy showed mild axon loss and no evidence of myelin wide-spacing. Normal levels of plasma neurofilament light chain on serial measurements, flaccid quadriplegia with no bulbar involvement, lack of upper motor neuron signs, and EMG and CSF findings meeting the 2021 EAN/PNS criteria of CIDP, led to a diagnosis of CIDP-MAG. Treatment with plasma exchange followed by IVIG resulted in partial recovery.
Conclusions:
CIDP-MAG can present with progressive quadriparesis and minimal clinical sensory abnormalities, mimicking ALS. Treatment response to plasma exchange and/or IVIG but not Rituximab or alkylating agents differentiates this entity from typical MAG neuropathy. A careful review of clinical presentation, electrophysiology, nerve biopsy features, and serum neurofilament light chain levels, is required to arrive at the correct diagnosis.
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