Cause: inhalation of fungus Coccidioides immitis

Endemic to: Mexico, South America, southwestern USA

Histo: chronic granulomatous process in bones, joints, periarticular structures

Location:

1. bones: most frequently in metaphyses of long bones + medial end of clavicle, spine, ribs, pelvis / bony prominences of patella, tibial tuberosity, calcaneus, olecranon, acromion
2. arthritis of weight-bearing joints (33%):
   Location: ankle, knee, wrist, elbow
   • “desert rheumatism” = immune-complex–mediated arthritis
3. tenosynovitis of hand, bursitis

• focal areas of destruction, formation of cavities (early) = bubbly bone lesion
• bone sclerosis surrounding osteolysis (later, rare)
• proliferation of overlying periosteum
• destruction of vertebra with preservation of disk space
• psoas abscess indistinguishable from tuberculosis, may calcify
• joints rarely infected (usually monoarticular from direct extension of osteomyelitic focus): synovial effusion, juxtaarticular osteopenia, bone destruction, rice bodies, joint space narrowing late in disease, ankylosis
• soft-tissue abscess (common)

DDx: tuberculosis