What are the reasons for doing derm+IM instead of just derm? Is it more out of intellectual interest?
Several students who I talked to that matched into derm said that they were actually considering IM at one point. What are the similarities between the two fields that would lead someone to consider both? If you considered both at one point, why did you decide on derm?
First, dermatology may be a separate residency, but it really is part of internal medicine. Derm has tremendous overlap with A/I, heme/onc, med genetics, and rheumatology. In my case, I was heavily considering IM and rheum or heme/onc. I picked derm because it allows me to dip into all of these fields, I like the fast pace, I prefer clinic to the inpatient service, and I can see complex cases without having to go through a soul-crushing three year medicine residency.
I interviewed for derm-only at several programs that have or have had med-derm spots, and based on my interactions with faculty and current residents, there are two groups of people who do med-derm. The first do med-derm because they want an academic derm spot where a big part of their job will be doing inpatient consults. The second group wants to do med-derm because they want to manage complex diseases like cutaneous lymphoma, bullous diseases, and connective tissue disorders.
IMHO, you do not need an extra year-and-a-half of training to feel comfortable doing either path, but I can understand how extra IM training will make someone feel more comfortable doing inpatient consults. I do not, however, understand why one would need extra IM training to feel comfortable managing complex derm cases. What one does need is to train at a program that offers derm-only residents exposure to complex derm cases and management with complex therapies (all biologics, thalidomide, dapsone, chlorambucil, targretin, PUVA, photopheresis, etc). The weird thing is that the programs that offer med-derm programs (Penn, Harvard, Northwestern, University of Minnesota, and, until recently, University of Wisconsin) are all very large derm programs with major hospitals and affiliated med schools that are in the top 30 for NIH funding. Therefore, even derm-only residents at these programs should have extensive exposure to complex cases and management.
One last thing: at my interviews, I was amazed by how many faculty members were willing to state behind closed-doors that they thought their department's med-derm spots were unnecessary.