<s>[INST] My son is 6 years old and on warfarin for a single vertircle repaired post Fontan heart leasion. We noticed a bruise on his arm 2 days ago. It is getting bigger, reddish pink on the outside ring and white in the middle. It is also raised in the middle. Trying to figure out if it is a bite or he just wacked his arm weird at school. Any advice? [/INST] Hi... Thank you for consulting in Chat Doctor. As he is on warfarin it could be a subcutaneous bleeding which going on. But, Skin conditions are best diagnosed only after seeing directly. I suggest you to upload photographs of the same on this website, so that I can guide you scientifically. Hope my answer was helpful for you.  I am happy to help any time. Further clarifications and consultations on Chat Doctor are welcome. If you do not have any clarifications, you can close the discussion and rate the answer. Wish your kid good health. </s>