It will not be problematic for rheum, endo, ID, nephro, palliative, sleep or similar less competitive specialties. You probably won't match to do your fellowship at UCSF, but if you show an interest in rheumatology, get a couple letters, you'll be fine.
1 year fellowship can be done after pulm, or after straight IM... or after FM, psych, neuro, or even ENT. I have a few friends who went straight IM->Sleep.
I think the job market isn't as good, so if you don't have pulm to do it with people do part time sleep part time PCP.
It will not be problematic for rheum, endo, ID, nephro, palliative, sleep or similar less competitive specialties. You probably won't match to do your fellowship at UCSF, but if you show an interest in rheumatology, get a couple letters, you'll be fine.