IM/any specialty to Derm can be pretty tough. Agree that choosing Derm from the get-go in medical school is the better option as there are other issues that come up with applicants switching from a residency to another residency (like not having time to make connections, prepare an application or interview, burning bridges w/ current program) or completing a residency then doing a second residency (lack of Medicare funding for the second residency- though I don't really know how much of a problem funding ends up being for larger institutions). If you are already in a residency, try to utilize your existing Derm connections through electives and research, go to grand rounds and get to know everyone, look for volunteer opportunities like skin cancer screening events, try to bridge your current residency with dermatology like in research and teaching. Feel free to PM me if you have more questions.