Clinical Characteristics of Parkinsonism in HTLV-1-Associated Myelopathy

Human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is the classic neurological manifestation of HTLV-1 infection; however, this virus has also been associated with other neurological disorders. Concurrent parkinsonism is relatively rare and presents diagnostic challenges. The present study aimed to identify the clinical characteristics of HAM/TSP with parkinsonism.

This retrospective study included HAM/TSP patients hospitalized in Kagoshima University Hospital from January 2000 to March 2022. Clinical and laboratory findings of the HAM/TSP patients with parkinsonism (P-HAM) were collected from the medical records and compared with HAM/TSP patients without parkinsonism (typical HAM/TSP [T-HAM]). P-HAM cases were defined as patients presenting with any combination of rigidity, resting tremor, bradykinesia, and/or postural instability, with these symptoms not attributed to HAM/TSP.

Of 246 HAM/TSP patients, 11 (4.5%) presented with parkinsonism. Compared with T-HAM, the age of onset was significantly older (65.0 vs. 48.8 years, p = 0.001) in patients with P-HAM. Moreover, despite a shorter illness duration (8.5 vs. 12.5 years, p = 0.151), the Osame Motor Disability Score was significantly higher in P-HAM cases than in T-HAM cases (6.3 vs. 4.6, p = 0.0132), and all P-HAM cases had scores ≥ 4. Laboratory findings showed no differences between the groups.

In our cohort, 4.5% of HAM/TSP patients had concomitant parkinsonism, which was associated with a later age of onset and greater disease severity. The coexistence of parkinsonism in HAM/TSP may be underrecognized, and our findings expand the clinical spectrum of neurological disease with HTLV-1 infection.