A 35-year-old man presented after experiencing a 5-minute episode of generalized tonic-clonic seizure 3 days earlier. No other accompanying symptoms were reported. He had experienced painless decrease of vision in both eyes for 6 years but did not seek medical care. He had had hypertension for 3 years, with amlodipine taken regularly. A sibling developed uremia in their 30s. A parent died of kidney failure in their 40s. On results of an ophthalmic examination, his best-corrected visual acuity was 20/50 OD and 20/40 OS, without visual field defects, dyschromatopsia, or relative afferent pupillary defect. Extraocular movements were intact. Neurologic examination findings were unremarkable except for mild cognitive impairment. Fundus fluorescein angiography showed retinal vasculitis (Figure, A). Enhanced magnetic resonance imaging (MRI) of the brain showed diffuse white matter hyperintensities—leukoencephalopathy—with multiple ring-enhancing lesions (Figure, B). Results of routine blood tests were significant for kidney insufficiency (proteinuria, 3.47 g of protein in 24 hours; estimated glomerular filtration rate, 38.5 mL/min). Angiotensin-converting enzyme level and serum tumor marker findings were normal. Infection panel screenings for hepatitis, HIV, syphilis, tuberculosis, and parasites were negative. Antinuclear antibodies and antineutrophil cytoplasmic antibodies were negative. Whole-body positron emission tomographic/computed tomographic (PET/CT) imaging detected no hypermetabolic changes. The cerebrospinal fluid (CSF) profiling, including cytologic analysis, was normal. Culture of the CSF and blood was negative for bacteria and fungus.