Reversible cerebral vasoconstriction syndrome (RCVS) is a syndrome characterized by severe headache with segmental vasoconstriction of the cerebral arteries that resolves within 12 weeks. A 16-year-old girl with refractory cytopenia of childhood, who was receiving the immunosuppressant cyclosporine, developed severe headache and was diagnosed with RCVS using magnetic resonance imaging, includin...