This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Pathology
IL-6 is persistently raised in?- 
Select and explain. 
A. Kawasaki disease, B. Viral encephalitis, C. HIV encephalitis, D. Behcet's disease
D: Behcet's disease
Answer: D: Behcet's disease 
Explanation: Increased cerebrospinal fluid (CSF) IL-6 has been repoed in patients with Behcet's disease (BD) and neurological involvement. CSF IL-6 seems to be a marker of disease activity and long-term outcome for pNB along with CSF cell count and protein levels. CSF IL-6 could be used in chronic progressive patients who have normal CSF cell, or protein levels to detect disease activity. Ref: Medscape