Of the 38 patients negative for RFC1 expansion, a likely cause for their neuropathy was found in 11: one had had chemotherapy, one had an elevated HbA1c in the diabetic range, four had monoclonal antibodies (one of whom also had low vitamin B12), another had low vitamin B12, three had high titre ANA, and one was found to have a history of nitrous oxide abuse. Here, BTG3 is linked to neuropathy.