Neuro-Behçet Disease, Neuro-Sweet Disease, and Spectrum Disorders.

Behçet disease and its related disorder, Sweet disease, are multifactorial disorders whose susceptibility loci have been identified in the genes of various immunological factors aside from human leukocyte antigens. The neurological involvement of these diseases, including encephalitis, myelitis, and meningitis, referred to as neuro-Behçet disease (NBD) and neuro-Sweet disease (NSD) respectively, is sometimes difficult to diagnose, especially when the characteristic mucocutaneous symptoms do not precede neurological symptoms or when characteristics of both diseases are present in a single patient. NBD and NSD constitute a spectrum of diseases that are differentiated according to the combination of risk factors, including the genetic background. Encephalitis, myelitis, and meningitis similar to NBD or NSD can be diagnosed as spectrum disorders, even if the characteristic mucocutaneous symptoms fail to be detected. Understanding these conditions as a disease spectrum may help elucidate the disease pathogenesis and assist in the development of therapeutic agents.