A strong trend ( p = 0.0077) toward a difference in the age of onset was largely driven by the small subgroup with monoclonal gammopathy (type 5), which were older than the others (in agreement with the higher incidence of gammopathies in older patients).
Infectious ( Borrelia Burgdoferi , viral meningitis, herpes zoster being the most frequent) comorbidities were significantly over-represented in patients with OCB type 2 and 3 ( p < 0.001); inflammatory conditions (systemic autoimmune diseases including thyroiditis, arthritis and, in one case, multiple sclerosis) were more prevalent in patients with OCB type 2 and 3 (11 and 14%) compared to patients without OCB, but the finding did not reach statistical significance ( p = 0.23).