[Central nervous system leukemia mimicking rapidly progressive HTLV-1 associated myelopathy]

A 79-year-old woman was suffered from rapidly progressive paresthesia of lower limbs and gait disturbance. After one month, she showed flaccid paraplegia and hyperreflexia in the lower limbs with positive Babinski signs. Anti-HTLV-1 antibody titer was elevated in the serum, but negative in the cerebrospinal fluid (CSF). CSF examination showed mild pleocytosis, elevated protein, and normal glucose content. Adult T cell lymphoma (ATL)-like cells were seen in the CSF. MRI showed no abnormal intensity in the spinal cord and brain. Two months later, she showed rapid worsening of the paraplegia and she became unable to stand. A tentative diagnosis of rapidly progressive HTLV-1 associated myelopathy (HAM) was given, but intravenous methylprednisolone was ineffective. Six months later, she developed pneumonia, and abundant ATL cells were seen in the peripheral blood, suggesting a diagnosis of ATL. Direct infiltration of ATL cells to central nervous system was therefore suggested to have caused neurological abnormalities in this case. One may consider central nervous system leukemia when rapidly progressive HAM-like symptoms and signs are recognized, especially without positive anti-HTLV-1 antibody in the CSF.