Medicine & USMLE


  1. Histoplasma
  2. Blastomyces
  3. Coccidioides
  4. Paracoccidioides
  5. Tinea (Dermatophytes)
  6. Malassezia
  7. Candida albicans
  8. Aspergillus fumigatus
  9. Cryptococcus neoformans
  10. Mucor and Rhizopus
  11. Pneumocystis jirovecii
  12. Sporothrix schenckii


Coccidioides is a fungi that is responsible for causing infections in the Southwestern part of the United States. It is a dimorphic fungi, taking on the form of a mold outside the body and a large spherule filled with endospores inside the human body. Coccidioides is endemic to the Southwestern US and is specifically associated with inhalation of spores in dust. Infections with Coccidioides causes Coccidioidomycosis, which is also known as San Joaquin Valley Fever or simply Valley Fever. Patients typically present with  pneumonia, arthralgias, and skin manifestations such as erythema nodosum and erythema multiforme. Histopathology of affected tissues reveal granulomas and fungal spherules filled with endospores. While treatment for mild infections is supportive, severe infections can be treated with fluconazole or itraconazole for local symptoms and Amphotericin B for severe systemic infections.

Key Points

  • Coccidioides spp.
    • Includes C. immitis, C. posadasii
    • Characteristics
      • Dimorphic fungi
        • Exists as a mold in the soil, outside body (20ºC)
        • Exists as a large spherule inside body tissues (37ºC)
          • Unlike other mycoses, which exist as yeasts in tissues
          • exists as spherules in human tissues. Spherules are covered by a capsule and contain endospores.
    • Transmission
      • Endemic to southwestern US
        • South-central Arizona, the San Joaquin Valley and adjacent areas of California, regions of southern Nevada and Utah, southwestern New Mexico, and western Texas
        • Associated with dust exposure in endemic areas (e.g. archeological digs, earthquakes)
      • Inhalation of spores
      • Cannot be transmitted from person to person (unlike TB)
    • Presentation
      • Causes Coccidioidomycosis
        • Pneumonia
          • Fever, dry cough, with pulmonary infiltrates, hilar adenopathy
          • May resemble acute TB
        • Arthralgias (desert rheumatism)
          • symmetric arthralgias, particularly of the ankles, knees, and wrists
        • Skin manifestations
          • Erythema nodosum (desert bumps)
            • painful, erythematous nodules on the lower extremities
          • Erythema multiforme
            • Hypersensitivity reaction with a typical target lesion
            • Seen in a necklace distribution
    • Diagnosis
      • Histopathology
        • Spherule filled with endospores of Coccidioides
          • Much larger than RBC
        • Can form granulomas (like TB)
      • Detection of anti-coccidioidal antibodies in serum is used
    • Treatment
      • In healthy patients with mild infections, antifungal agents is not indicated
      • Fluconazole or itraconazole for local severe infection
      • Amphotericin B for systemic severe infection