<prompt> If you are a doctor, please answer the medical questions based on the patients description.I have a 9 cm lymphnode and my doctor put me on an antibiotic to see if the swelling will go down. It s so far not working and now I have a very swollen and very painful bump on my birthmark near where my leg and butt meet but inner and it s purple and red like.  <response>: Hi, Dear,Thanks for the query to My Chat Doctor Clinic. I studied your query in depth. I feel concerned about the worry you expressed. In my opinion-the painful-bump non-responding to antibiotics-is-mostly-a Lipoma at the Sacral Dimple with a subdued spina bifida underneath a purple-reddish-Birthmark.? Ant thats why antibiotics not working-for the pain.?or could be Colonial Sinus ? I would advise -MRI study of the bump and consultation with a pediatric surgeon and ortho-surgeon and or-neuro-surgeon- who as a team could be of help in planning right treatment. The pain does not appear to be due to infection inflammation, but is due to the stretching of the neural fibers around the lipoma over a spina bifida, which is the possibility from the facts of the query. Hope this would help your query. Wehe ll come for more queries to Chat Doctor. Have a good day. 