[Case of neuro-Behçet disease with HLA-B54, Cw1, which is difficult in clinical diagnosis from neuro-Sweet disease].

The patient was a 53-year-old woman with an 18-year history of recurrent oral aphtae, genital ulcers and folliculitis-like erupsions without mucocutaneus symptoms. She was admitted to our hospital for headache, and presented with meningeal irritation, dysarthria and right pyramidal signs. Brain MRI showed abnormal intensities extending from the right midbrain to the bilateral corona radiata, accompanied by contrast enhancement. She was diagnosed as having an incomplete form of neuro-Behçet disease (NBD) based on the diagnostic criteria for NBD. However, the HLA-type was defined as B54 and Cw1, which is common and specific in neuro-Sweet disease (NSD). Oral administration of prednisolone was markedly effective for the neurological symptoms and improved radiological findings, suggesting NSD rather than NBD as the clinical diagnosis for this patient Since she presented with clinical features that appeared in both diseases, the definitive diagnosis was clinically difficult. While tapering the dosage of prednisolone, we carefully observed the appearance of skin lesions and erythema nodosum appearing on her right lower leg. Skin biopsy demonstrated the features of erythema nodosum: lobular panniculitis with the accumulation of neutrophils and lymphocytes with necrotic fatty cells in the subcutaneous area, which was compatible with skin lesions in NBD. In our case, pathological findings of the skin lesion were required to differentiate between NBD and NSD, indicating the need for careful follow-up of dermatologic signs appearing in such a case.