Clinical course of neurogenic bladder dysfunction in human T-cell leukemia virus type-1-associated myelopathy/tropical spastic paraparesis: a nationwide registry study in Japan

Abstract

Background: Most patients with human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) develop neurogenic bladder dysfunction. However, longitudinal changes and treatment effects remain poorly understood. This study aimed to characterize the clinical course of urinary dysfunction in this population.

Methods: This prospective observational study included 547 patients enrolled in HAM-net, a nationwide registry for HAM/TSP in Japan. Urinary dysfunction severity was evaluated using the HAM/TSP-bladder dysfunction symptom score (HAM-BDSS) and the HAM/TSP-bladder dysfunction severity grade (HAM-BDSG). These specific measures were recently developed for assessing urinary dysfunction in HAM/TSP. We analyzed longitudinal changes over a 6-year follow-up period, associations between urinary and gait dysfunction, and treatment efficacy of urinary catheterization and mirabegron (a β3-adrenergic agonist for overactive bladder symptoms).

Results: The mean (standard deviation [SD]) age and disease duration at enrollment were 61.9 (10.7) years and 16.6 (11.6) years, respectively, and 74.6% of patients were women. Only 8.0% were free from urinary symptoms (HAM-BDSG 0), 65.4% had urinary symptoms or were on medication (HAM-BDSG I), and 23.2% and 3.3% used intermittent and indwelling catheters (HAM-BDSG II and III), respectively. HAM-BDSG and BDSS were worse in patients with greater gait dysfunction (p < 0.001 for both). During the 6-year follow-up, 66.7% of patients with HAM-BDSG 0 developed new urinary symptoms. Of those with HAM-BDSG I at enrollment, 10.8% started using urinary catheters. Importantly, HAM-BDSS significantly improved after initiating catheterization (mean [SD] change, - 8.93 [10.78], p < 0.001). The number of patients receiving mirabegron increased in the fourth year. Multivariable linear regression analysis significantly associated mirabegron with improvement in HAM-BDSS (- 5.82, 95% confidence interval - 9.13 to - 2.51, p = 0.001).

Conclusions: Urinary dysfunction affected 92% of patients and progressed over the 6-year follow-up. Urinary symptoms were more severe in patients with poorer gait function. Urinary catheterization and mirabegron were effective in relieving symptoms. Effective utilization of real-world data is key to establishing evidence for rare diseases, such as HAM/TSP.

Keywords: Human T-cell leukemia virus type 1; Human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis; Mirabegron; Neurogenic bladder; Urinary symptom score.