The Impact of LRRK2 G2019S on Parkinson's Disease: Clinical Phenotype and Treatment in Tunisian Patients

Objective LRRK2-G2019S is the most frequent mutation in North African Parkinson's disease (PD) patients. Data on its impact on disease progression and treatment response remain elusive. Therefore, we investigated the clinical features, treatments, and complications of PD in Tunisian patients according to their LRRK2-G2019S profile. Methods This longitudinal retrospective study was performed in the Department of Neurology, Razi University Hospital. We included clinically diagnosed PD patients according to the Movement Disorders Society criteria and reviewed their medical records for clinical, treatment, and neuropsychological assessments. All patients were screened for the LRRK2-G2019S mutation using Sanger sequencing. The correlation between LRRK2-G2019S and clinical PD features was evaluated. Results We included 393 PD patients, 41.5% of whom had LRRK2-G2019S mutations. Patients with mutations were younger (p = 0.017), and female PD patients had a greater mutation frequency (p = 0.008). Mutation carriers exhibited distinct clinical features, with a greater frequency of postural instability gait difficulty forms (adjusted-p < 0.001). During disease progression, carriers showed a faster annual progression in the Unified Parkinson's Disease Rating Scale Section III scores (adjusted-p = 0.009), and significantly higher levodopa equivalent dose values in later stages (1060.81 vs. 877.83 for 6-8 years). Motor complications, such as dyskinesia (adjusted-p < 0.001) and motor fluctuations (31.9% vs. 25.7%, adjusted-p < 0.001), were more prevalent in carriers, particularly in the later stages. LRRK2-G2019S carriers also exhibited a lower prevalence of non-motor symptoms, including episodic memory (adjusted-p < 0.001), attention (adjusted-p < 0.001), and dysexecutive disorders (adjusted-p = 0.038), as well as neuropsychiatric symptoms and dysautonomic signs. Conclusion The present study demonstrated that the variability of the clinical profile among Tunisian PD patients was explained by the incomplete penetrance of LRRK2-G2019S, which increased with age. Further studies using biomarker and disease data are to PD