All deep chested and large breeds - including GSMD- are at risk of spleen or gastric torsion (bloat). Some GSMD may have "delicate stomach" causing digestion problems, others urinary system issues - these reguire specific diets. Peculiar symptom observed occassionaly is "floor licking' - affected dog vigorously licks some objects or surface (floor, carpet etc.) or eats grass -it indicates that dog is having a form of heartburn and needs to be given an antiacid. This happens most often to young dogs and puppies.
Some pedigree lines in Europe and USA can have cases of epilepsy - please make sure you buy your GSMD from reputable breeder.