The LRRK2-G2019S mutation is the most common cause of PD in North Africa. G2019S-PD has been described as similar to idiopathic with minor clinical differences.

We recruited 107 G2019S-carriers and 119 non-carriers. Patients carrying mutations in other PD-genes were excluded. Levodopa-equivalent daily dose was calculated according to the conversion table proposed by Tomlinson et al. The percentage of improvement was calculated as follows: (baseline score - lowest score after medication) x100/baseline score. Phenotypes were classified into three sub-groups – tremor dominant (TD), postural instability gait disorder (PIGD), or indeterminate phenotypes – according to the published formulas of Jankovic et al.  Logistic regression models adjust for age, PD duration and levodopa daily doses were used to compare clinical features between the studied groups.

The daily doses of levodopa were similar between G2019S carriers and non-carriers (adjust p-value = 0.56). The mean response to treatment rate was 81.2% for G2019S carriers and 74% for non-carriers (adjust p-value = 0.26). In the G2019S carrier group, the PIGD group had a lower dose of levodopa treatment of 656 mg/day than non-IPGD group (706.3 mg/day), but this difference was not significant (adjust p-value = 0.5). The difference in the mean response to treatment rate was also not significant 96% for PIGD phenotype and 80% for non-PIGD group (adjust p-value = 0.95).

G2019S carriers are known to tend to be treated with higher dose of levodopa with better response to treatment than idiopathic. However, in this study, both levodopa doses and improvement were similar in G2019S carriers and non-carriers. This may be related to an interference of particular genetic factors in our population.