Microbiology · Year 2 · from Microbiology
Case 3: Coccidioidomycosis (Valley Fever)
Presentation
A 42-year-old previously healthy man presents with 3 weeks of cough, low-grade fever, fatigue, and chest pain. He recently returned from Arizona where he was working on a construction project in the desert. He also reports painful red nodules on his shins and joint aches. Chest radiograph shows right hilar lymphadenopathy and a right lower lobe infiltrate. Examination reveals tender erythematous nodules on the anterior shins bilaterally. CBC shows eosinophilia (12%). Coccidioides IgM antibodies are positive.
Clinical Image
Left: Erythema nodosum - tender erythematous nodules on the shins, a reactive phenomenon in acute coccidioidomycosis associated with good prognosis. Right: Histopathology showing a Coccidioides spherule filled with endospores.
Image Source: Lecture image - coccidioidomycosis clinical and pathologic findings
Questions
- What is the diagnosis, and what exposure history is significant?
- What is the significance of the skin findings and eosinophilia?
- Does this patient require antifungal treatment?
- What complications should be monitored for, and who is at high risk?
Answers
- Diagnosis and exposure: This is acute pulmonary coccidioidomycosis (Valley fever) caused by Coccidioides species, acquired through inhalation of arthroconidia during construction work in the endemic desert southwest (Arizona). The organism is found in arid soils, and infection risk increases with soil disruption (construction, dust storms, earthquakes). Approximately 60% of infections are asymptomatic; symptomatic cases present 1-3 weeks after exposure with flu-like illness and pneumonia.
- Significance of skin findings and eosinophilia:
- Erythema nodosum (and erythema multiforme, arthralgias) represent immune-mediated reactive phenomena called "desert rheumatism" or "Valley fever arthritis"
- Paradoxically, these are good prognostic signs indicating a robust cell-mediated immune response that will likely control the infection
- Eosinophilia is common in coccidioidomycosis and can suggest fungal infection in the appropriate clinical context
- Erythema nodosum is NOT due to fungal skin involvement - skin lesions in disseminated disease appear different (papules, nodules, plaques, draining sinuses)
- Treatment decision: For uncomplicated acute pulmonary coccidioidomycosis in healthy patients with good immune response (as suggested by erythema nodosum):
- Observation without antifungal therapy may be appropriate - most cases are self-limited
- However, treatment with fluconazole or itraconazole for 3-6 months is often given to reduce symptom duration and prevent complications
Treatment is definitely indicated for:
- Severe disease (extensive infiltrates, respiratory failure)
- Prolonged symptoms (>6-8 weeks)
- High-risk patients (immunocompromised, pregnant, diabetes, Filipino or African American ancestry)
- Disseminated disease
- High complement fixation titers (>1:16)
- Complications and high-risk groups: Complications:
- Chronic pulmonary disease: Cavitary lesions that may cause hemoptysis or pneumothorax
- Dissemination (<1% of cases in healthy hosts): Skin, bones/joints, meninges
- Coccidioidal meningitis: Most serious complication; requires lifelong fluconazole; high mortality
High-risk groups for severe/disseminated disease:
- HIV/AIDS (especially CD4 <250)
- Organ transplant recipients
- Patients on TNF-alpha inhibitors
- Pregnancy (especially third trimester)
- Filipino and African American ancestry (genetic susceptibility)
- Diabetes mellitus