Ver el código de «Template:Fever of unknown origin DDX»

====Infections (~30%)====
*'''Abscess'''
**Intra-abdominal [[abscess]] (hepatic, subphrenic, pelvic, perinephric)
**[[Epidural abscess]]
**Dental abscess
**[[Prostatitis]]
*'''Endovascular'''
**[[Endocarditis]]
**Infected vascular graft/device
**Mycotic aneurysm
*'''Mycobacterial'''
**[[Tuberculosis]] (pulmonary and extrapulmonary)
**Nontuberculous mycobacteria (MAC)
*'''Viral'''
**[[EBV]] (mononucleosis)
**[[CMV]]
**[[HIV]] (acute seroconversion)
**[[Hepatitis B]], [[hepatitis C]]
**[[COVID-19]]
*'''Fungal'''
**[[Histoplasmosis]]
**[[Coccidioidomycosis]]
**[[Blastomycosis]]
**[[Cryptococcosis]]
**[[Aspergillosis]] (immunocompromised)
*'''Parasitic'''
**[[Malaria]]
**[[Toxoplasmosis]]
**Visceral leishmaniasis
**Amebiasis (liver abscess)
*'''Bacterial'''
**[[Osteomyelitis]]
**[[Pyelonephritis]]/renal abscess
**[[Cholangitis]]
**[[Sinusitis]] (chronic)
**[[Brucellosis]]
**[[Q fever]] ([[Coxiella burnetii]])
**[[Lyme disease]]
**[[Cat scratch disease]] (''Bartonella'')
**[[Syphilis]]
**[[Whipple's disease]]
**[[Rat-bite fever]]

====Malignancy (~20%)====
*'''Hematologic''' (most common malignant cause of FUO)
**[[Lymphoma]] (Hodgkin and non-Hodgkin)
**[[Leukemia]] (especially acute leukemia)
**Multiple myeloma
**Myelodysplastic syndrome
**Castleman disease
*'''Solid Tumors'''
**Renal cell carcinoma
**Hepatocellular carcinoma
**Colon cancer
**Pancreatic cancer
**Atrial myxoma
**Pheochromocytoma

====Autoimmune/Inflammatory (~20%)====
*'''Connective Tissue Disease'''
**[[Adult-onset Still's disease]] (AOSD)
**[[Systemic JIA]] (sJIA) — pediatric equivalent
**[[Systemic lupus erythematosus]] (SLE)
**[[Rheumatoid arthritis]]
**[[Polymyositis]]/dermatomyositis
**Mixed connective tissue disease
*'''Vasculitis'''
**Giant cell (temporal) arteritis / polymyalgia rheumatica (especially adults >50)
**[[Polyarteritis nodosa]]
**Granulomatosis with polyangiitis (Wegener's)
**Eosinophilic granulomatosis with polyangiitis (Churg-Strauss)
**Takayasu arteritis
**[[Kawasaki disease]] (pediatric)
*'''Granulomatous'''
**[[Sarcoidosis]]
**Crohn's disease / [[inflammatory bowel disease]]
*'''Autoinflammatory/Periodic Fever Syndromes'''
**[[Familial Mediterranean fever]]
**TNF receptor-associated periodic syndrome (TRAPS)
**Hyper-IgD syndrome (HIDS)
**PFAPA syndrome (pediatric)
**Schnitzler syndrome
*'''Other'''
**[[Macrophage activation syndrome]] (MAS) / [[hemophagocytic lymphohistiocytosis]] (HLH)
**Kikuchi-Fujimoto disease (histiocytic necrotizing lymphadenitis)

====Drug Fever====
*[[Antibiotics]] (beta-lactams, sulfonamides, nitrofurantoin)
*[[Anticonvulsants]] (phenytoin, carbamazepine)
*[[Allopurinol]]
*[[Heparin]]
*Procainamide
*[[DRESS syndrome]]
*[[Serotonin syndrome]]
*[[Neuroleptic malignant syndrome]]
*Chemotherapy/biologic agents

====Endocrine/Metabolic====
*[[Thyrotoxicosis]] / [[thyroid storm]]
*[[Adrenal insufficiency]]
*[[Pheochromocytoma]]
*Hypertriglyceridemia (rarely)

====Thromboembolic/Vascular====
*[[Pulmonary embolism]]
*[[Deep vein thrombosis]]
*Hematoma (retroperitoneal, intramuscular)
*Aortic dissection (rarely)

====Factitious/Habitual====
*Factitious fever (self-induced)
*Munchausen syndrome / Munchausen by proxy (pediatric)

====Miscellaneous====
*Post-surgical/post-procedural inflammation
*[[Gout]]/pseudogout (crystal arthropathy)
*Cirrhosis / [[alcoholic hepatitis]]
*Hemolytic anemia
*Transfusion reaction
*[[Tissue necrosis]] (rhabdomyolysis, large hematoma, pancreatitis)
*Hypothalamic dysfunction (central fever)
*Periodic fever of unknown cause (~10-15% of FUO never diagnosed)