Snapshot A 55-year-old woman presents to the emergency room with a 5-month history of worsening back pain. She recently immigrated from Japan and has a history of sexually transmitted diseases, each successfully treated. She reports that she has had a backache for the past few months, as well as an increasingly unstable gait resulting in falls, heaviness in her lower extremities, and difficulty climbing stairs. On physical exam, there is symmetric proximal muscle weakness in her thighs and generalized hyperreflexia. Imaging of the spine is normal. Serologic testing is positive for a retrovirus. Introduction Classification human T-cell lymphotropic virus type 1 (HTLV-1) icosahedral capid, segmented, enveloped, single-stranded, positive-sense RNA virus clinical syndromes adult T-cell leukemia/lymphoma myelopathy/tropical spastic paraparesis transmission parenteral sexual vertical Epidemiology incidence most common in Japan, Africa, South America, and Caribbean risk factors unprotected sexual intercourse multiple sexual partners increased age female sex Prognosis most are asymptomatic if symptomatic, the prognosis is poor Presentation Adult T-cell leukemia/lymphoma hypercalcemia hepatosplenomegaly lymphadenopathy skin lesions variable morphologies Myelopathy/tropical spastic paraparesis backache unstable gait heaviness in the lower extremities lower limb proximal muscle weakness hyperreflexia loss of control of bladder sphincter Imaging Brain magnetic resonance imaging (MRI) myelopathy/tropical spastic paraparesis periventricular and subcortical white matter changes Studies Labs detection of anti-HTLV-1 antibodies via ELISA detection of genomic RNA via RT-PCR complete blood count > 5% abnormal lymphocytes Peripheral blood smear adult T-cell leukemia/lymphoma "flower" cells Making the diagnosis based on clinical presentation and laboratory studies Differential Mycosis fungoides distinguishing factor generalized pruritus with well-demarcated erythematous plaques Treatment Medical zidovudine + interferon-α indication first-line therapy chemotherapy indication alternate first-line therapy corticosteroids indication myelopathy/tropical spastic paraparesis Complications Opportunistic infections