Clinical features of human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy (HAM) are predominantly consistent with cord pathology. Imaging and autopsy studies have also demonstrated brain inflammation in HAM though this is generally subclinical. Six cases (of whom four had HAM) have previously been reported with encephalopathy in HTLV-1 infected patients, without alternative identified aetiology. Histopathology was reported in three of these, with perivascular CD8 +lymphocytic infiltrates in the brain, similar to that seen in the spinal cord in HAM.
We describe three further cases of encephalitis in the UK HAM cohort (n=142). Clinical features included: reduced consciousness; fever/hypothermia; headache; seizures; focal neurology. Investigation showed: raised CSF protein; pleocytosis; raised CSF:peripheral blood mononuclear cell HTLV-1 proviral load ratio; MRI either normal or showing diffuse, partially reversible leucoencephalopathy. No alternative aetiology was found. Two died following 1–5 recurrent episodes over a period of 1–5 years, despite responses to immunosuppression.
We reviewed the existing literature together with our new cases. 7/9 had concurrent HAM. All seven deteriorated sub-acutely preceding encephalopathy. 7/9 were treated with IV steroids, six improved. Six died, five despite steroids.
We propose that HTLV-associated encephalopathy may be part of the spectrum of disease seen in HAM itself.
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