PLXNA4 and Parkinson disease: Further, even taken together additional evidence highlighting PLXNA4 p.Ser657Asn (suggestive linkage signal, high conservation and predicted pathogenicity, excess of very rare coding variants in cases and functional considerations) can be viewed as suggestive at best and by no means exclude the possibility of other causative or modifying genetic factors that play a role in the PD phenotype in our family.