Novel Parkinson Subtype System Predicts Disease Duration, Severity

Parkinson disease (PD) subtypes derived from a novel subtyping system were significantly linked with disease duration and severity. However, the system may solely reflect stages of PD, rather than identify distinct clinical subtypes.

Published in Parkinsonism & Related Disorders, researchers indicate that as patients with PD (PwP) exhibit varied clinical subtypes that determine disease severity and progression, grouping these distinct PD subtypes could prove beneficial in personalizing care for patients.

In 2015, a framework was proposed that would divide PD into 3 subtypes, mild motor-predominant (MM), diffuse-malignant (DM), and intermediate. These classifications were based on factors relating to motor severity, cognitive dysfunction, dysautonomia, and rapid eye movement behavior disorder. Although promising, research has suggested that these subtypes might reflect different stages of the same disease over time and not how the disease may progress.

These researchers sought to explore the influence of disease duration and stage on these novel clinical subtypes by deriving data from a cross-sectional cohort of 122 PwP. Patients were classified as having the MM (n = 49), DM (n = 29), or intermediate (n = 44) subtype, with the relationship between either disease duration or stage, as measured by the Hoehn and Yahr staging, and subtype allocation being explored.

When comparing disease duration, on average, the MM subtype exhibited the shortest (3.75 years), while the longest was shown to be for the DM subtype (11.04 years). The intermediate subtype fell in between (5.11 years).

Additionally, disease subtypes were linked with PD duration, with 58.34% of those classified as having the MM subtype receiving their diagnosis ≤5 years ago compared with only 5% of those with the DM subtype. Conversely, those with the DM subtype were more likely to have received their diagnosis ≥10 years ago (51.61%) compared with 22.58% of those who had the MM subtype.

“Since a patient with [the] MM phenotype at onset will be likely to convert into the DM phenotype at some point, the implication is made that a particular subtype is not able to predict if certain milestones will be reached or not,” said the study authors. “On the other hand, the current data also show that a proportion of patients have reached the DM stage with short disease duration, which supports the notion that a difference in the rate of progression exists among [patients with PD].”

They note that their study findings may not suggest that these subtypes reflect mutually exclusive disease pathways, so further longitudinal studies are warranted.

Reference

Erro R, Picillo M, Scannapieco S, et al. The role of disease duration and severity on novel clinical subtypes of Parkinson disease [published online March 22, 2020]. Parkinsonism Relat Disord. doi: 10.1016/j.parkreldis.2020.03.013.