Emerging parkinsonian phenotypes.

There is no unique way to define Parkinson's disease (PD) clinically. "Classical parkinsonian features" can be found not only in sporadic idiopathic PD patients, but also in other parkinsonian disorders, such as genetic forms associated with mutations in PARK or in other genes. The present review will describe the parkinsonian phenotypes emerging from the new Mendelian genes which have been linked to PD (such as PARK9 and PARK14), the associated dystonia-parkinsonism disorders (such as the syndromes of neurodegeneration with brain iron accumulation) and the emerging data on heterozygous variants of genes which could influence the risk to develop PD and the PD phenotypes (like PD associated with glucose cerebrosidase mutations).