Ethical approval
The study was approved by the Institutional Review Board.
Informed consent
All subjects in whom molecular studies were performed provided written informed consent.
Funding
This work was supported by University of Zagreb research grant to RK [BM068 - project 1101439].
Potential conflict of interest
The authors report no conflicts of interest. The authors are responsible for the content and writing of this article online at http://dx.doi.org/10.1080/10428194.2017.1296146.