Background: The natural history of HTLV-1-associated myelopathy (HAM) has been mainly described in HTLV-1 endemic countries such as Japan, Brazil and Martinique.
Objectives: The authors describe the natural history of the largest cohort of patients with HAM living in the UK from 1993 to 2007.
Methods: Prospective, longitudinal study comparing clinical and virological outcome between first and last clinical visit. Incidence and cause of death were documented and the mortality calculated.
Results: 48 patients were included: 79.2% were female, 79.2% were of Afro-Caribbean origin, and 83.3% acquired HTLV-1 through breastfeeding or unprotected heterosexual intercourse. The mean age of onset was 46 years. The median durations from onset of symptoms to diagnosis and to last follow-up were 2 and 11.6 years. The median time of follow-up was 3.8 years. The most common first recalled symptom was unilateral leg weakness. The median times from onset to unilateral, bilateral walking aid and frame or a wheelchair were 11, 11.2, 11.3 and 18 years. The overall average deterioration in timed walk in patients whose need for aid did not change was 2 s/10 m/year. Three patients progressed rapidly and were unable to walk within 2 years. Six patients were slow/non-progressors. The mortality was 2.4/100 person year follow-up. The median HTLV-1 viral load remained unchanged at 14%.
Conclusions: HAM is a slowly progressing chronic disease. Timed walk deteriorates by 2 s/10 m/year, and patients remain ambulant for 10 years but become wheelchair-dependent a decade later. HTLV-1 viral load remains high and unchanged over time regardless of clinical progression.