Neuro‐Sweet's disease

Sweet’s syndrome (SS) can appear in extracutaneous lesions and when the central nervous system is involved, the condition is termed neuro-Sweet’s disease (NSD). A 32-year-old man presented with a 4-day history of headache, facial rash, fever, and sore throat (Fig. 1a). Laboratory examinations showed a white blood cell count of 11 9 10/l with 84% neutrophils and serum Creactive protein 981 nmol/l (normal 0.76–28.5). A biopsy specimen showed papillary dermal edema with dense neutrophilic infiltration in the dermis without vasculitis (Fig. 1b). Workups for hematologic and internal malignancies, and autoimmune diseases showed no positive findings. He was positive for HLA-B54 and Cw1 and negative for B51. The diagnosis of classical SS was made. He was treated with oral prednisolone at 30 mg (0.5 mg/kg) daily. His symptoms improved promptly in 2 weeks, and the prednisolone was tapered and suspended within 3 months. After 2 years, the patient had a sudden consciousness disorder accompanied by fever. Laboratory examinations showed a white blood cell count of 23.6 9 10/l with 89% neutrophils and C-reactive protein 209 nmol/l. He was disoriented about his name and birth date, and attention and verbal memory were remarkably reduced, and he showed marked irritability. Neurological examinations were otherwise normal. Brain magnetic resonance imaging (MRI) revealed abnormal signal intensity areas in the right caudate nucleus, bilateral cortex of the temporal lobe, and left cortex of the frontal lobe (Fig. 2). A cerebrospinal fluid (CSF) sample showed pleocytosis at 382 9 10/l (44% lymphocytes, 56% neutrophils) and mildly elevated protein at 0.47 g/l (normal 0.10–0.40). CSF and serological examinations for bacteria, fungi, and various viruses were unremarkable. Relapsed facial edematous erythemas with sterile pustules suggested that the indefinite encephalitis should be NSD. His symptoms remarkably improved with 1 g/day intravenous methylprednisolone pulse therapy for 3 days, followed by oral prednisolone at 60 mg/day. The prednisolone has been tapered, and he has since remained asymptomatic with prednisolone 7.5 mg/day and dapsone 75 mg/day. The proposed diagnostic criteria for NSD requires a steroid-responsive or self-remitting encephalomeningitis with the clinical manifestations of SS, and an absence of cutaneous vasculitis, thrombosis, and uveitis, which are typical of Behc et’s disease. NSD affects both sexes almost equally, and age of onset is between 30 and 70 years. NSD presents with various neurological symptoms depending on the affected regions, including encephalitis, meningitis, headache, conscious disturbance, epilepsy, hemiparesis, tetraparesis, psychiatric disorders, and dyskinesia. Brain MRI reveals high signal intensity lesions with no predilection by the T2-weighted and fluidattenuated inversion recover sequences. A CSF sample usually shows a mildly elevated protein concentration and mild to moderate pleocytosis with a predominance of lymphocytes. In NSD cases, recurrences are frequent. Therefore, prolonged low-dose corticosteroids and/or corticosteroid-sparing agents, including colchicine, potassium iodide, and dapsone may be required to prevent recurrences. Differentiation from neuro-Behc et’s disease (NBD) is often problematic. NSD and NBD may have an identical appearance on MRI particularly in the basal ganglia and