A case of childhood unilateral relapsing primary angiitis of the central nervous system.

The patient was a 17-year-old girl with transient right-sided weakness and dysesthesia associated with headache and nausea. Head magnetic resonance imaging (MRI) revealed white matter lesions confined to the left hemisphere. Initially, multiple sclerosis was suspected, and methylprednisolone (mPSL) pulse therapy was administered, followed by fingolimod hydrochloride. However, on day 267, the patient again experienced transient hypesthesia. Cranial MRI showed expansion of the highly infiltrated areas of the left hemisphere on fluid-attenuated inversion recovery (FLAIR) and T2 weighted image, accompanied by edema. Multiple contrasting areas were also observed. Susceptibility-weighted imaging demonstrated several streaks and some corkscrew-like appearances with low signals from the white matter to the cortex, suggestive of occluded or dilated collateral vessels. Multiple dotted spots indicating cerebral microbleeds (MBs) were also observed. A brain biopsy revealed lymphocytic, non-granulomatous inflammation in and around the vessels. Vascular occlusion and perivascular MBs were prevalent. The patient was diagnosed with relapsing primary angiitis of the central nervous system (PACNS), and immunosuppressive treatment was initiated, mPSL 1000 mg/day pulse therapy. The patient's clinical symptoms and neuroradiological abnormalities gradually improved. She is now receiving oral prednisolone (6 mg/day) and mycophenolate mofetil (1750 mg/day). This case corresponds to unilateral relapsing, which has recently been reported as a specific clinicopathological subtype of PACNS.