- Coccidioidomycosis, also known as San Joaquin Valley fever, is a systemic fungal infection endemic to parts of the southwestern United States and elsewhere in the Western Hemisphere. Small pockets (i.e. southeast Washington state) may exist throughout the west.
- Residence in and recent travel to these areas are critical elements for the accurate recognition of patients who develop this infection.
- The most common syndrome to come to medical attention is a community-acquired pneumonia (CAP), often associated with a variety of rheumatologic, cutaneous, or systemic complaints.
- Differences in disease severity are thought to be predominantly the consequence of differences in the immunologic responses to infection among individuals.
- Urban areas within endemic regions of Arizona have demonstrated that coccidioidal infection accounted for 24% of newly diagnosed CAP in ambulatory patients.
- The most common initial syndrome is that of a respiratory illness with signs and symptoms typical of pneumonia — fever, drenching night sweats, and weight loss. Often the most striking systemic symptom is that of extreme fatigue.
- The usual incubation period for early coccidioidal syndromes is from 1–4 weeks.
- In some patients with early coccidioidal infection, dermatologic or rheumatologic complaints may dominate their illness. Both erythema nodosum and erythema multiforme occur in coccidioidomycosis.
- Rheumatologic complaints are typically arthralgias of multiple joints, generally symmetrical, more of the distal lower extremities, and almost never associated with detectable joint effusions.
- Hematogenous spread beyond the lungs normally occurs within weeks to several months following infection.
- Exceptions to this estimate are immunosuppressed patients with more remote prior exposure or patients who have previously been treated with an antifungal drug for primary pulmonary infection in whom relapses occurred up to 4 years after treatment had been stopped.
- The signs and symptoms of disseminated coccidioidal lesions vary widely depending upon their location. Importantly, pulmonary symptoms or radiographic abnormalities may be minimal or completely absent.
- Although patients with deficiencies in cellular immunity are especially susceptible to severe coccidioidomycosis including dissemination, most patients with coccidioidal lesions outside of the lungs have no identified immune deficiencies.
- Enzyme immunoassays (EIAs) for anticoccidioidal immunoglobulin M (IgM) and immunoglobulin G (IgG) are commercially available.
- When done to evaluate a clinical illness, any positive test result for anticoccidioidal antibodies is usually associated with a recent or active coccidioidal infection, in contrast with serologic tests for many other types of infection where diagnostic IgG antibodies often are detectable for life.
- An important limitation of all coccidioidal serologic tests is that they may be negative and even persistently negative despite an early coccidioidal infection being present.
- EIA is often used for initial screening because of its increased sensitivity. However, if not confirmed by the more specific but less sensitive immunodiffusion test, the diagnosis is less certain. Repeat testing is often useful to resolve this uncertainty.
- Patients who have already developed extrapulmonary coccidioidal lesions nearly always exhibit anticoccidioidal antibodies in their serum, regardless of whether tested by EIA, immunodiffusion or complement fixation titration. Severely immunosuppressed patients may be exceptions to this rule.
Culture and Histopathology
- An alternative approach to diagnosing early coccidioidal infection is to isolate the fungus in culture, which may be the only means of establishing a diagnosis since serologic evidence may take weeks and even months to develop.
- The diagnosis of disseminated coccidioidomycosis should usually rely on the histopathologic identification in, or fungal isolation from, an extrapulmonary lesion.
- Needle aspiration has been a very valuable approach.
- One common exception is the diagnosis of coccidioidal meningitis (CM) as discussed below.
Additional Evaluation at the Time of Initial Diagnosis
- If a careful review of systems and physical examination do not identify focal extrapulmonary problems, additional laboratory or imaging evaluation is usually unnecessary to fully assess extent of disease.In contrast, new or progressive focal signs or symptoms warrant further assessment appropriate for the anatomic location to detect dissemination.