Signs and Symptoms
Rocky Mountain spotted fever can be very difficult to diagnose in its early stages, even among experienced physicians who are familiar with the disease.
Patients infected with R. rickettsii generally visit a physician in the first week of their illness, following an incubation period of about one to two weeks after a tick bite. The early clinical presentation of Rocky Mountain spotted fever is nonspecific and may resemble a variety of other infectious and non-infectious diseases.
Initial symptoms may include:
fever
nausea
emesis
severe headache
muscle pain
lack of appetite
Later signs and symptoms include:
maculopapular rash
petechial rash
emesis
abdominal pain
joint pain
The classic triad of findings for this disease are fever, rash, and history of tick bite. However, this combination is often not identified when the patient initially presents for care. The rash has a centripetal,or "inward" pattern of spread, meaning it begins at the extremities and courses towards the trunk.
The rash first appears 2-5 days after the onset of fever and is often not present or may be very subtle when the patient is initially seen by a physician. Younger patients usually develop the rash earlier than older patients. Most often it begins as small, flat, pink, non-itchy spots (macules) on the wrists, forearms, and ankles. These spots turn pale when pressure is applied and eventually become raised on the skin. The characteristic red, spotted (petechial) rash of Rocky Mountain spotted fever is usually not seen until the sixth day or later after onset of symptoms, but this type of rash occurs in only 35% to 60% of patients with Rocky Mountain spotted fever. The rash involves the palms or soles in as many as 50% to 80% of patients; however, this distribution may not occur until later in the course of the disease. As many as 10% to 15% of patients may never develop a rash.
Abnormal laboratory findings seen in patients with Rocky Mountain spotted fever may include thrombocytopenia, hyponatremia, or elevated liver enzyme levels.
Rocky Mountain spotted fever can be a very severe illness and patients often require hospitalization. Because R. rickettsii infects the cells lining blood vessels throughout the body, severe manifestations of this disease may involve the respiratory system, central nervous system, gastrointestinal system, or renal system. Host factors associated with severe or fatal Rocky Mountain spotted fever include advanced age, male sex, African-American race, chronic alcohol abuse, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Deficiency of G6PD is a sex-linked genetic condition affecting approximately 12% of the U.S. African-American male population; deficiency of this enzyme is associated with a high proportion of severe cases of Rocky Mountain spotted fever. This is a rare clinical course that is often fatal within 5 days of onset of illness.
Long-term health problems following acute Rocky Mountain spotted fever infection include partial paralysis of the lower extremities, gangrene requiring amputation of fingers, toes, or arms or legs, hearing loss, loss of bowel or bladder control, movement disorders, and language disorders. These complications are most frequent in persons recovering from severe, life-threatening disease, often following lengthy hospitalizations.
