• Infection with parasite Babesia microti (U.S.). Babesia divergens (Europe)

• Transmitted by Ixodes Epidemiology

• Europe & U.S. (more commonly coastal areas & islands off of MA. NY. Rl. CT)

• Peak incidence spring and summer Clinical manifestations

• Range from asx to fevers, sweats, myalgias. & headache to severe hemolytic anemia.

hemoglobinurea. & death

• Risk factors for severe disease include asplenia, depressed cellular immunity. * age


• Blood smear with intraerythrocytic parasites; PCR; serology (late) Treatment

• [Atovaquone - azithromycin] or [clindamycin • quinine]

• Exchange transfusion if parasitemia >10%, severe hemolysis, or SIRS



• Fever >101°F or >38.5°C on more than one occasion

• Duration weeks

• No diagnosis despite 1 wk of intensive evaluation Etiologies

• Differential extensive, but following are some of the more common causes

• More likely to be subtle manifestation of common disease than an uncommon disease

• In Pts with HIV: 75% infectious, rarely due to HIV itself

• Up to 30% of cases undiagnosed, most spontaneously defervesce


Etiologies of Classic FUO

Infection -30%

Tuberculosis: disseminated or extrapulmonary disease can have normal CXR. PPD. sputum AFB; biopsy (lung, liver, bone marrow) for granulomas has 80-90% yield in miliary disease Endocarditis: consider HACEK organisms. Bartonella. Legionella. and CoxieHa

Intra-abdominal abscess: hepatic, splenic, subphrenic, pancreatic.

perinephric, pelvic, prostatic, appendicitis Osteomyelitis, dental abscess, sinusitis, paraspinal abscess CMV. EBV. Lyme disease, malaria, babesiosis, amebiasis, fungal infxn

Connective tissue disease -30%

Giant cell arteritis: headache, scalp pain, jaw claudication, visual disturbances. PMR, T ESR Adult onset Still's disease (juvenile rheumatoid arthritis): fevers with evanescent, salmon-colored macular truncal rash during fevers may precede arthritis Polyarteritis nodosa, other vasculitides RA. SLE

Neoplasm -20%

Renal cell carcinoma: microscopic hematuria. T Ha

Hepatocellular carcinoma, pancreatic cancer, colon cancer

Atrial myxomas: obstruction, embolism, constitutional symptoms Leukemia, myelodysplasia

Miscellaneous -20%

Drugs, factitious DVT. PE. hematoma

Thyroid, adrenal insufficiency, pheochromocytoma Granulomatous hepatitis, sarcoidosis

Familial Mediterranean fever (mutation in pyrin in myeloid cells; episodic fever, peritonitis, pleuritis; T WBC & ESR during attacks)

(loncct 1997;350:S75; Archives 2003:163:545. 1033) Workup

• History: fever curve, infectious contacts, travel, pets, occupation, medications, thorough

ROS.PMHx and PSHx.TB history

• Discontinue unnecessary medications (only 20% w/ med-induced FUO will have eosinophilia or rash); reassess 1-3 wks after meds d/c'd

• Careful physical exam with attention to skin findings. LAN. murmurs. HSM. arthritis

• Laboratory evaluation

CBC with diff. lytes. BUN. Cr. LFTs. ESR. CRP. ANA. RF. cryoglobulin. LDH BCx x 3 sets (off abx; hold for HACEK. RMSF. Q fever. Brucella). U/A. UCx. PPD. heterophile Ab. CMV antigenemia test. HIV Ab test (PCR if 1° infxn suspected)

• Imaging studies: CXR. chest & abdominal CT (oral & IV contrast). ? tagged WBC or gallium scan. I FDG PET. ? echocardiogram

• Consider temporal artery bx if Î ESR and age 60. particularly if other s/sx

• ? Bone marrow aspirate and bx (esp if signs of marrow infiltration) or liver bx (especially if

Î Ad>):even w/o localizing signs or symptoms, yield may be up to 15%


• Empiric antibiotics are not indicated (unless Pt neutropenic)

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