CD40LG and peripheral neuropathy: Given the concern for peripheral neuropathy in the setting of MGUS, an anti-MAG antibody assessment was done which returned positive (MAG-SGPG or myelin-associated glycoprotein sulfate-3-glucuronyl paragloboside antibody titer = 1:51,200, MAG IgM antibody titer = 1:25,600). His hospital course was complicated by worsening respiratory insufficiency resulting in hypercapnic respiratory failure requiring non-invasive ventilation.