Lots of options to combine with genetics: OBGYN-maternal fetal medicine, oncology, dermatology, endocrinology, cardiology, neurology, ophthalmology, ENT, psych... I recently met someone who is combining emergency med with genetics (this may be more of a career change than a true combo though, I didn't ask). Probably you can figure out what you are drawn towards during your clinical training and don't have to have it all decided at this point. Basically most areas in medicine you can imagine (and probably some you can't) can be tied into genetics. However, length of training is a consideration for many, so that is also something to keep in mind.