Pathophysiology

1) Rickettsial infection caused by Coxiella burnetii 2) acute and chronic forms exist

Signs and Symptoms

1) Severe headache 2) fever/chills/sweats 3) myalgias 4) extreme fatigue 5) dry cough 6) hepatosplenomegaly 7) nausea/vomiting 8) in immunocompetent hosts usually self-limited over 10-14 days 9) chronic form almost always involves endocarditis with a wide variety of other syndromes (see below)

Characteristic Test Findings

Radiology – 1) chest radiograph shows focal bronchopneumonia 2) CT scan shows “doughnut ring” pattern in liver parenchyma Laboratory – 3) positive rheumatoid factor 4) increased erythrocyte sed rate 5) increased C-reactive protein 6) increased gamma-globulin 7) thrombocytopenia initially followed by reactive thrombocytosis 8) diagnosis is by positive serology via indirect immunofluorescence

Histology/Gross Pathology

1) organism is small, pleomorphic, gram-negative coccobacillus 2) liver granulomata

Associated Conditions

chronic form has increased incidence of – 1) endocarditis 2) pericarditis 3) myocarditis 4) hepatitis 5) pancreatitis 6) deep vein thrombophlebitis 7) optic neuritis 8) Guillain-Barre syndrome 9) SIADH 10) orchitis 11) lymphadenopathy 12) erythema nodosum

Biochemistry

organism enters cells after being phagocytocized by macrophages

Inheritance/Epidemiology

1) infection is via inhalation, drinking infected milk, or contact with infected products of gestation (placenta) 2) vectors are goats, sheep, and cattle 3) most commonly found in butchers, veterinarians, and dairy workers 4) person-to-person contact is possible 5) initial presentation varies by geographical region – pneumonia in Canada and hepatitis in France

Treatment

1) acute disease – doxycycline for 2-3 weeks 2) chronic form – doxycycline and rifampin for 18-36 months

Tips for USMLE

1) unlike most rickettsial infections, there is usually no skin rash 2) WBC are usually normal 3) if sheep herder in France develops severe headache, fever, chills with enlarged tender liver, inflamed blood clots in his left calf, and a platelet count of 800,000/dL, think Q fever