COCCIDIOIDOMYCOSIS

Coccidioides is a dimorphic fungus that is a common cause of respiratory tract infections in southwestern United States. The area of endemicity stretches from southern California to western Texas. Coccidioides immitis is limited to the San Joaquin valley region of southern California, whereas Coccidioides posadasii is responsible for disease occurring outside of California and in Central America and South America.²³

Both cell-mediated and humoral immunity are induced following infection with C immitis. Whereas high humoral immunity (high IgG level) generally corresponds with a poor outcome, increased cell-mediated immunity (a positive skin test result) portends a good response.²⁴ Infections are acquired following the inhalation of arthroconidia.²⁵

In patients with CD4⁺ lymphocyte counts of less than 250/μL, both localized pneumonia and disseminated infection are observed.⁴ The incidence of coccidioidomycosis has decreased with the introduction of potent ART.²⁶ In the pre-ART era, the incidence rate of coccidioidomycosis in areas where the causative organism was endemic was 2% to 5%.

In persons with hematological malignancy, coccidioidomycosis can cause severe illness, with a high risk of disseminated infections and death. In a retrospective review of patients who have bone marrow disease or hematological malignancy and coccidioidomycosis, the most common underlying malignancies were non-Hodgkin lymphoma and chronic lymphocytic leukemia.²⁷

Patients who have undergone organ transplant are at the greatest risk for infection in the first year after the procedure.²⁴ The risk is increased in persons who have a history of infection or in whom serological test results are positive just before transplant. ²⁸ Another risk factor for coccidioidomycosis after SOT is receipt of antirejection therapy.²⁹ Infection can occur through reactivation of preexisting latent infection, newly acquired infection related to living in or traveling to areas where Coccidioides is endemic, or secondary transmission of an infected organ. Posttransplant reactivation is the most commonly described mechanism of infection.²² Disseminated disease is common.

In HIV-1–infected patients, presentation with diffuse pulmonary disease, usually with a reticulonodular pattern, is common and can resemble Pneumocystis pneumonia. Clinical symptoms include fever, night sweats, and dyspnea.^24,26 A similar presentation is often seen in patients with hematological malignancy.²⁷ In SOT recipients, the presentation of pulmonary infection varies from an acute illness with fever, productive cough, and dyspnea to shock and fulminate respiratory failure. Patients also may present with more insidious symptoms such as fatigue, anorexia, and weight loss without any pulmonary symptoms.²⁸