If i have thrombocytopenic will i bruise if i get a mosquito bite?

Not usually: It is unusual to get a bruise from a mosquito bite even if the platelet count is quite low. It all depends, however, on how low the platelet count and if you have taken anything else that might further inhibit platelet function such as Aspirin or other nsaids. It also depends on if you are vigorously scratching the bite area since that can do much more to promote local bruising as well.