Rocky Mountain Spotted Fever - Symptoms and Diagnosis

Symptoms and Diagnosis

Spotted fever can be very difficult to diagnose in its early stages, and even among experienced physicians who are familiar with the disease find it hard to detect.

People infected with R. rickettsii usually notice symptoms following an incubation period of 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:

• Fever
• Nausea
• Emesis (vomiting)
• Severe headache
• Muscle pain
• Lack of appetite
• Parotitis in some cases (somewhat rare).

Later signs and symptoms:

• Maculopapular rash
• Petechial rash
• 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 two to five days after the onset of fever, and it is often quite subtle. Younger patients usually develop the rash earlier than older patients. Most often the rash 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 percent of patients with Rocky Mountain spotted fever. The rash involves the palms or soles in as many as 80 percent of the patients. However, this distribution may not occur until later on in the course of the disease. As many as 15 percent 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 or Caribbean background, chronic alcohol abuse, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Deficiency of G6PD is a sex-linked genetic condition affecting about 12 percent of the Afro-American male population. Deficiency in this enzyme is associated with a high proportion of severe cases of Rocky Mountain Spotted Fever. This is a rare clinical complication that is often fatal within five days of the onset of the disease.

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.