This patient has a number of risk factors for neuropathy: H/O B12 deficiency, hypothyroidism, renal failure, exposure to colchicine. B12 deficiency causes a distal axonal neuropathy 1, and is not a good explanation for segmental demyelination. The significance of mild elevation of voltage gated potassium channel is also unclear, given that the patient has a progressive demyelinating neuropathy (the clinical phenotypes associated with voltage gated potassium antibodies include nerve hyperexcitability syndrome, neuromyotonia, limbic encephalopathy, Morvan’s syndrome) 2 .
The differential diagnosis for this patient include chronic inflammatory demyelinating polyneuropathy (CIDP), and POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes) syndrome. POEMS syndrome (and not CIDP) is a multi-system disease, and skin changes, renal failure, edema and hypothyroidism are all consistent with that diagnosis. Click here for further diagnostic workup and diagnosis.
References
1. Fine EJ, Soria E, Paroski MW, Petryk D, Thomasula L. The neurophysiological profile of vitamin B12 deficiency. Muscle & nerve. Feb 1990;13(2):158-164.
2. Montojo MT, Petit-Pedrol M, Graus F, Dalmau J. Clinical spectrum and diagnostic value of antibodies against the potassium channel related protein complex. Neurologia. Jan 29 2014.