= multisystemic zoonosis of worldwide distribution; endemic in Middle East (Arabian Peninsula), South and Central America, Mediterranean region (Spain, Italy)

Organism: small gram-negative nonmotile, nonsporing, aflagellate, nonencapsulated coccobacilli: Brucella abortus, B. suis, B. canis, B. melitensis

Mode of transmission:

• handling contaminated animal products (in excreta of infected animals like urine, stool, milk, products of conception) or consuming dairy products from unpasteurized milk

Histo: small intracellular pathogens cause small noncaseating granuloma within RES

Location: commonest site of involvement is reticuloendothelial system; musculoskeletal system

• 1–3 weeks between initial infection + symptoms
  • Radiologic evidence of disease in 69% of symptomatic sites!

• Brucellar spondylitis (53% = most common site)
  Age: 40 years is average age at onset
  • pain, localized tenderness, radiculopathy, myelopathy
  
  Location: lumbar (71%) >thoracolumbar (10%) >lumbosacral (8%) >cervical (7%) >thoracic (4%)
  1. focal form
     • bone destruction at diskovertebral junction (anterior aspect of superior endplate)
     • associated with bone sclerosis + anterior osteophyte formation + small amount of gas
  2. diffuse form: entire vertebral endplate / whole vertebral body affected with spread to adjacent disks + vertebral bodies
     • bone destruction associated with sclerosis
     • small amount of disk gas (25–30%)
     • facet joint involvement
     • obliteration of paraspinal muscle-fat planes
     • paraspinal abscess (smaller than in TB)
     • no / minimal epidural extension
     
     DDx: TB (paraspinal abscess, gibbus)
• Extraspinal disease
  1. Brucellar synovitis (81%)
     Location: knee >sacroiliac joint >shoulder >hip >sternoclavicular joint >ankle >elbow
     Site: organism localized in synovial membrane
     • serosanguinous sterile joint effusion
     • bilateral sacroiliitis
  2. Brucellar destructive arthritis (9%)
     • indistinguishable from tuberculous / pyogenic arthritis
  3. Brucellar osteomyelitis (2%)
     • pain, tenderness, swelling
  4. Brucellar myositis (2%)

Dx: serologic tests (enzyme-linked immunosorbent assay, counterimmunoelectrophoresis, rose bengal plate test

Rx: combination of aminoglycosides + tetracyclines

DDx: fibrous dysplasia, benign tumor, osteoid osteoma