Posterior reversible encephalopathy syndrome in ANCA-associated vasculitis

Abstract

Fuentes and colleagues described a case with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis suspected to be complicated by posterior reversible encephalopathy syndrome (PRES) [1]. This adds to the accumulating evidence that PRES may be associated with ANCA-associated vasculitis. However, we have some concern about the diagnosis of this case. PRES (also termed reversible posterior leukoencephalopathy syndrome, RPLS) represents a clinical and radiological syndrome characterised by reversible vasogenic oedema [2] in the posterior brain, which primarily arises from autoregulation failure and endothelial dysfunction [3]. The reversible vasogenic oedema, as most specifically and sensitively detected by apparent diffusion coefficient (ADC) map of diffusion-weighted imaging (DWI), preferably involving posterior white matter, and typical clinical manifestations like acute onset of headache, confusion or decreased level of consciousness, visual disturbance and seizures can help to diagnose a typical PRES. Although lesions might be revealed by T2-weighed imaging (T2WI) or fluid attenuated inversion recovery images (FLAIR) of magnetic resonance imaging (MRI), they are not specific for vasogenic oedema [4]. Atypical cases are not rare [3], whereas they should be diagnosed with caution, especially after rigid exclusion of other confounding disorders. Differential diagnoses of PRES include metabolic encephalopathy, inflammatory demyelinating diseases, vasculitis, etc. Connective-tissue diseases, including systemic lupus erythematosus (SLE), polyarteritis nodosa, Wegener’s granulomatosis, microscopic polyangiitis, Henoch Schonlein purpura, Takayasu’s arteritis and thrombotic thrombocytopenic purpura, have been suggested as disorders in which PRES can develop [1, 5–7]. The central nervous system (CNS) complications in connective-tissue diseases are not uncommon, which include vasculitis [8], acute or subacute infarction [9] and PRES [1, 5–7]. Demyelination, inflammatory lesions, ischaemia or oedema may present as reversible changes in the brain as revealed by neuroimaging modalities. Therefore, reversibility, not only clinical but radiological, and vasogenic oedema as detected by ADC map of DWI, as well as well-established risk factors predisposing to hypertension, such as phaeochromocytoma, glomerulonephritis, eclampsia and receiving cytotoxic and immunosuppressant drugs [3], should be confirmed by clinical and neuroimaging examinations to diagnose this case as a typical PRES. In summary, PRES represents a clinicoradiological syndrome, the diagnosis of which relies on typical clinical and neuroimaging findings.