Late appearance of skin rash in Rocky Mountain spotted fever.

Late appearance of a skin rash in Rocky Mountain spotted fever is associated with a high mortality. Our patient's rash appeared 14 days after the onset of illness, during his recovery. In endemic areas one must rely on clinical clues other than rash to raise the suspicion of Rocky Mountain spotted fever. The combination of fever, headache, myalgias, marked left shift in the differential white blood cell count, severe thrombocytopenia, and hyponatremia all help to suggest the correct diagnosis early in the course of the illness.