Abstract
A 66-year-old female developed progressive gait instability over a 5–10 year period with difficulty climbing stairs. Associated symptoms included bilateral leg cramping and long-standing urinary incontinence requiring multiple bladder surgeries. She had no sensory disturbance in the lower limbs and no involvement of the face or upper limbs. An older sister developed similar symptoms at age 58. The patient was born to non-consanguineous parents in Chile and migrated to Australia aged 40. Examination revealed a spastic gait with impaired tandem walking and positive Romberg’s sign. Lower limb examination revealed bilateral spasticity, mild symmetric proximal weakness, global hyperreflexia, extensor plantar responses, and impaired distal vibration sense. Brain and whole spine MRI demonstrated several non-specific supratentorial white matter hyperintensities without cord signal change or atrophy. Somatosensory evoked potentials showed conduction time delay between lumbar and cervical levels from lower but not upper limbs . Routine blood tests including metabolic, autoimmune and infectious screen were negative. A genetic panel for hereditary spastic paraparesis was negative. Cerebrospinal fluid analysis revealed normal protein (0.19g/L), 1x10^6/L mononuclear cell, negative multiplex meningitis PCR, positive oligoclonal bands, and negative NMO/MOG antibody. CSF HTLV-1 DNA by PCR revealed 1,110,531 copies/million peripheral blood mononuclear cells. CSF:serum HTLV-1 antibody ratio was 1.04:1, indicative of intrathecal synthesis. A diagnosis of HTLV-1 associated myelopathy (HAM), also known as tropical spastic paraparesis, was confirmed. At the time of writing, the patient is considering whether to pursue treatment with steroids and mogamulizumab, an anti-CCR4 monoclonal antibody with Phase II evidence of clinical and serological benefit.
