Sorry to hear about your diagnosis at such a young age.
I also am classified as young onset and have a family history of Parkinson’s that goes back four generations. I have been tested for the two most common genetic mutations (variants of the genes LRRK2 and GBA) that came back negative and am now undergoing more comprehensive genetic testing that I expect will establish a rarer genetic defect as a contributory factor.
A few comments on the above (to the best of my understanding - I am not a medical professional):
(1) There are quite a number of variants in certain genes known to increase the risk of developing PD. There is a list here: https://panelapp.genomicsengland.co.uk/panels/108/ and new ones are still being discovered.
(2) Carrying one of these variants does not guarantee that you will get PD - as with many things in life, it’s a combination of genes, environment and luck that results in a condition developing. In particular, even if you have passed a faulty gene onto a child, it does not guarantee that the child will develop PD later in life.
(3) Genetic defects can very occasionally arise from spontaneous mutations, so if you carry a genetic variant it is not necessarily one that was passed down from your parents.
(4) Currently there are only generic treatments for PD like L-dopa but there is a growing realisation that PD may take different forms. Research into the genetically linked forms of PD hopes to develop more targeted treatments for these different forms of PD. See this video for more information: https://www.youtube.com/watch?v=6F-Bx7qjnSo
I have written about my own ongoing genetic journey on a blog here that may be of interest: https://shakingsteven.blogspot.co.uk/2018/01/faulty-dna_6.html.