Fever of Unknown Origin Differential Diagnoses
- Author: Kirk M Chan-Tack, MD; Chief Editor: Burke A Cunha, MD more...
Diagnostic Considerations
Approximately 5-15% of patients with fever of unknown origin (FUO) remain undiagnosed, even after extensive evaluations.
Hepatobiliary infections
Acute cholecystitis and gallbladder empyema can lead to a diagnosis of FUO because of the lack of right upper quadrant pain or jaundice, especially in elderly patients.
Osteomyelitis
The most common reason for misdiagnosis of osteomyelitis is the failure to consider the disease in a patient who is febrile with musculoskeletal symptoms.
Parasitic infections
If the physician is unaware of a history of recent travel to an endemic area and if the fever pattern is nonsynchronized, malaria can be missed as a cause of fever.
Drug fever
A history of allergy, skin rashes, or peripheral eosinophilia is often absent in cases of drug fever. Neither the fever pattern nor the duration of previous therapy is helpful in establishing the diagnosis.
Tuberculosis
Tuberculosis (TB) is usually considered in the FUO differential diagnoses; however, several factors may prevent a prompt diagnosis of TB. In TB, dissemination, which usually occurs in immunocompromised patients, may initially manifest as constitutional symptoms that lack localizing signs.
Collagen-vascular and autoimmune diseases
Consider PAN, RA, and mixed connective-tissue diseases in patients with FUO, because of the potential for nonspecific presentations in these diseases. Rheumatic fever can be difficult to diagnose, because it is rare in the developed world.
Conditions to consider in the diagnosis of FUO
Diseases to consider in patients with symptoms of FUO include the following, as well as the disorders in the Differentials subsection, below:
- Abdominal Abscess
- Actinomycosis
- Acute Lymphoblastic Leukemia
- Acute Myelogenous Leukemia
- Adenoviruses
- Adrenal Carcinoma
- Adrenal Insufficiency
- Amebiasis
- Amebic Hepatic Abscesses
- Atrial Myxoma
- Atypical Mycobacterial Infection
- Bacillary Angiomatosis
- Bacteroides Infection
- Bartonellosis
- Blastomycosis
- Brain Abscess
- Brucellosis
- California Encephalitis
- Campylobacter Infections
- Candidiasis
- Carcinoid Tumor, Intestinal
- C burnetii infection
- Chagas Disease (American Trypanosomiasis)
- Cholangitis
- Cholecystitis
- Choledocholithiasis
- Chronic Bacterial Prostatitis
- Chronic Lymphocytic Leukemia
- Chronic Mesenteric Ischemia
- Chronic Myelogenous Leukemia
- Clostridial necrotizing fasciitis
- Colon Cancer, Adenocarcinoma
- Coxsackieviruses
- Cryptococcosis
- Cytomegalovirus
- Cytomegalovirus Colitis
- Dengue Fever
- Diabetic Ulcers
- Drug Fever
- Eastern Equine Encephalitis
- Echoviruses
- Emphysematous Pyelonephritis
- Empyema, Gallbladder
- Empyema, Pleuropulmonary
- Enteroviruses
- Eosinophilic Pneumonia
- Eosinophilic Toxocariasis
- Epididymal Tuberculosis
- Epididymitis
- Epidural Abscess
- Erythema Multiforme (Stevens-Johnson Syndrome)
- Factitious Fever
- Gallbladder Gangrene
- Gastroenteritis, Viral
- Giardiasis
- Graves Disease
- Hairy Cell Leukemia
- Hepatitis A-E
- Hepatoma
- Herpes Simplex
- Histoplasmosis
- Human Immunodeficiency Virus
- Human Herpesvirus Type 6
- Hypersensitivity Pneumonitis
- Hyperthyroidism
- Inflammatory Bowel Disease
- Intra-abdominal Sepsis
- Japanese Encephalitis
- Kikuchi Disease
- Legionnaires Disease
- Leishmaniasis
- Leptospirosis
- Leukocytoclastic Vasculitis
- Libman-Sacks Endocarditis
- Listeria Monocytogenes
- Liver Abscess
- Lung Abscess
- Lymphocytic Choriomeningitis
- Lyssavirus Infection
- Malaria
- Malassezia furfur Infection
- Malignant histiocytosis
- Mastocytosis, Systemic
- Mediterranean Fever, Familial
- Mediterranean Spotted Fever
- Meningococcemia
- Miliary Tuberculosis
- Mucormycosis
- Mycoplasma Infections
- Naegleria Infection
- Neuroleptic Malignant Syndrome
- Nocardiosis
- Nonarticular Rheumatism/Regional Pain Syndrome
- Nonbacterial Prostatitis
- Norwalk Virus
- Onchocerciasis
- Osteomyelitis
- Pancreatitis, Acute
- Pelvic Inflammatory Disease
- Pericholangitis
- Pharyngitis, Viral
- Pneumonia, Viral
- Prostatic Abscess
- Psittacosis
- Q Fever
- Rat-bite Fever (S minor)
- Rhinocerebral Phycomycosis
- Sphenoid Sinusitis
- Thrombophlebitis
- Trypanosoma Infection
Differential Diagnoses
- Appendicitis
- Arenaviruses
- Aspergillosis
- Catscratch Disease
- Celiac Sprue
- Gout
- Graft Versus Host Disease
- Myocarditis
- Pericarditis, Acute
- Pericarditis, Constrictive
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