Idiopathic hypereosinophilic syndrome (IHES) is a primary haematological condition characterised by persistent, otherwise unexplained
hypereosinophilia sufficient to cause organ damage. Various neurological complications are reported, but very few have mentioned CNS pathology and none has included
CNS vasculitis. Our objective here is to report IHES as a new cause of histopathologically confirmed
CNS vasculitis. A 39-year-old man presented with a relapsing sub-acute
encephalopathy, with severe
headaches,
confusion and drowsiness,
myoclonus,
ataxia and papilloedema. He had a history of
nephrotic syndrome 18 years earlier, stable for the past 5 years on low-dose
corticosteroids and low-dose
tacrolimus (2 mg bd);
lichen planus, and (15 years previously) aloplecia totalis. On admission, he had a marked peripheral
eosinophilia (up to 9.1 × 10(9)/dL), which—it subsequently became clear—had been intermittently present for 16 years. After extensive investigation, biopsies of brain and bone marrow confirmed diagnoses of
cerebral vasculitis, with lymphocytic and macrophage (but not eosinophilic) cellular infiltration of blood vessel walls, and IHES.
CNS vasculitis can therefore now be added to the list of neurological complications of IHES. A dramatic and sustained neurological improvement, and likewise of the
eosinophilia, following treatment with
corticosteroids and
cyclophosphamide, emphasises the tractability of this newly described form of
CNS vasculitis.