title: Prevalence and clinical features of HTLV neurologic disease in the HTLV Outcomes Study.
abstract: BACKGROUND
  Almost 20 years after its discovery, the prevalence and clinical course of human T-lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM, also known as tropical spastic paraparesis [TSP]) remain poorly defined. Whereas the causative association of HTLV-I and HAM/TSP is generally recognized, controversy still surrounds the relationship between HTLV-II and HAM/TSP.
  
  
  METHODS
  The HTLV Outcomes Study (HOST-formerly Retrovirus Epidemiology Donor Study [REDS]) is a prospective cohort study including 160 patients with HTLV-I, 405 patients with HTLV-II, and 799 uninfected controls who have been followed every 2 years since 1990-1992. Clinical outcomes are measured by health interviews and examinations, and blood samples are obtained.
  
  
  RESULTS
  Six cases of HTLV-I-associated myelopathy (3.7%, 95% CI 1.4 to 8.0) and four cases of HTLV-II myelopathy (1.0%, 95% CI 0.3 to 2.5) have been diagnosed since the formation of the cohort. There have been no cases of HAM/TSP diagnosed among HTLV-negative subjects (0.0%, 95% CI 0.0 to 0.5). Clinical features of the cases include lower extremity hyperreflexia, variably associated with weakness, spasticity, and bladder dysfunction.
  
  
  CONCLUSIONS
  Systematic screening of HTLV-infected blood donors reveals a high prevalence of HAM/TSP. The clinical course of HAM/TSP appears highly variable. HTLV-II-associated myelopathy generally presents with milder and more slowly progressive signs and symptoms.
authors.affiliation: University of California San Francisco, Blood Centers of the Pacific, 94118, USA. orland@itsa.ucsf.edu
authors.forename: J R
authors.initials: JR
authors.lastname: Orland
authors.forename: J
authors.initials: J
authors.lastname: Engstrom
authors.forename: J
authors.initials: J
authors.lastname: Fridey
authors.forename: R A
authors.initials: RA
authors.lastname: Sacher
authors.forename: J W
authors.initials: JW
authors.lastname: Smith
authors.forename: C
authors.initials: C
authors.lastname: Nass
authors.forename: G
authors.initials: G
authors.lastname: Garratty
authors.forename: B
authors.initials: B
authors.lastname: Newman
authors.forename: D
authors.initials: D
authors.lastname: Smith
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Loughlin
authors.forename: E L
authors.initials: EL
authors.lastname: Murphy
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D015491:HTLV-II Infections / Q000175:diagnosis* / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D015493:Paraparesis, Tropical Spastic / Q000175:diagnosis* / Q000453:epidemiology*; D015995:Prevalence; D011446:Prospective Studies; D012307:Risk Factors