Reversible cerebral vasoconstriction syndrome in idiopathic multicentric Castleman disease under treatment with tocilizumab.

Background: Idiopathic multicentric Castleman disease (iMCD) is a rare polyclonal lymphoproliferative disorder characterised by systemic inflammation resulting from overproduction of interleukin 6 (IL-6). While iMCD primarily affects the lymph nodes and related tissues, it can also rarely involve the central nervous system. Case presentation: We report the case of a 58-year-old female patient with at least a 3-year history of iMCD, who experienced acute thunderclap headaches due to reversible cerebral vasoconstriction syndrome (RCVS). RCVS occurred 3 months after initiating treatment with tocilizumab, a humanised anti-IL-6 receptor monoclonal antibody, and was accompanied by focal cortical subarachnoid haemorrhage (SAH). Elevated IL-6 levels were found in both serum and cerebrospinal fluid. MR angiography revealed multiple diffuse stenotic lesions in the bilateral middle and posterior cerebral arteries, which, along with bilateral cerebral oedema, resolved within 3 months. The diffuse nature of the cerebral vasospasm and the presence of bilateral brain oedema suggested that cerebral vasospasm was due to RCVS rather than SAH. Conclusions: In patients with Castleman disease, RCVS may occur due to IL-6-dependent chronic cerebral vascular inflammation, either as a primary condition or as a complication of tocilizumab treatment.