Prolonged Fever Causes

Infections

• Bacterial (nonspecific):
  Abdominal abscess, adnexitis, apical granuloma, appendicitis, cholangitis, cholecystitis, diverticulitis, endocarditis, endometritis, epidural abscess, infected vascular catheter, infected joint prosthesis, infected vascular prosthesis, infectious arthritis, infective myonecrosis, intracranial abscess, liver abscess, lung abscess, malakoplakia (cystitis), mastoiditis, mediastinitis, mycotic aneurysm, osteomyelitis, pelvic inflammatory disease, prostatitis, pyelonephritis, pylephlebitis, renal abscess, septic phlebitis, sinusitis, spondylodiscitis, xanthogranulomatous urinary tract infection
• Bacterial (specific):
  Actinomycosis, atypical mycobacterial infection, brucellosis, Campylobacter infection, Chlamydia pneumoniae infection, chronic meningococcemia, gonococcemia, legionellosis, leptospirosis, listeriosis, Mycoplasma infection, rickettsiosis, Streptobacillus moniliformis infection, syphilis, tick-borne relapsing fever (Borrelia duttonii), tuberculosis, tularemia, typhoid fever and other salmonelloses, Whipple’s disease (Tropheryma whipplei)
• Fungal:
  Aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, cryptococcosis, histoplasmosis, Malassezia furfur infection, paracoccidioidomycosis, Pneumocystis jirovecii pneumonia, sporotrichosis, zygomycosis
• Parasitic:
  Amebiasis, babesiosis, echinococcosis, malaria, schistosomiasis, strongyloidiasis, toxocariasis, toxoplasmosis, trichinellosis, trypanosomiasis, visceral leishmaniasis
• Viral:
  coxsackievirus infection, cytomegalovirus infection, dengue, Epstein-Barr virus infection, hepatitis (A, B, C, D, E), herpes simplex, HIV infection, parvovirus infection

Noninfectious Inflammatory Diseases

• Systemic rheumatic and autoimmune diseases:
  Ankylosing spondylitis, autoimmune hemolytic anemia, autoimmune hepatitis, Behçet’s disease, cryoglobulinemia, dermatomyositis, gout, mixed connective-tissue disease, polymyositis, pseudogout, reactive arthritis, relapsing polychondritis, rheumatic fever, rheumatoid arthritis, Sjögren’s syndrome, systemic lupus erythematosus
• Vasculitis:
  Allergic vasculitis, giant cell vasculitis/polymyalgia rheumatica, granulomatosis with polyangiitis, hypersensitivity vasculitis, Kawasaki’s disease, polyarteritis nodosa, Takayasu arteritis, urticarial vasculitis
• Granulomatous diseases:
  Idiopathic granulomatous hepatitis, sarcoidosis
• Autoinflammatory syndromes:
  Adult-onset Still’s disease, Crohn’s disease, hemophagocytic syndrome, juvenile idiopathic arthritis, PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne), PFAPA syndrome (periodic fever, aphthous stomatitis, pharyngitis, adenitis), recurrent idiopathic pericarditis, SAPHO (synovitis, acne, pustulosis, hyperostosis, osteomyelitis)

Neoplasms

• Hematologic malignancies:
  Amyloidosis, angioimmunoblastic lymphoma, Hodgkin’s disease, hypereosinophilic syndrome, leukemia, lymphomatoid granulomatosis, malignant histiocytosis, multiple myeloma, myelodysplastic syndrome, myelofibrosis, non-Hodgkin’s lymphoma, plasmacytoma, systemic mastocytosis, vaso-occlusive crisis in sickle cell disease
• Solid tumors:
  Most solid tumors and metastases can cause fever. Those most commonly causing FUO are breast, colon, hepatocellular, lung, pancreatic, and renal cell carcinomas.
• Benign tumors:
  Angiomyolipoma, cavernous hemangioma of the liver, craniopharyngioma, necrosis of dermoid tumor

Miscellaneous

ADEM (acute disseminated encephalomyelitis), adrenal insufficiency, aneurysms, anomalous thoracic duct, aortic dissection, aseptic meningitis (Mollaret’s syndrome), atrial myxoma, cholesterol emboli, cirrhosis, complex partial status epilepticus, cyclic neutropenia, drug fever, extrinsic allergic alveolitis, factitious disease, fraudulent fever, Gaucher’s disease, Hamman-Rich syndrome (acute interstitial pneumonia), Hashimoto’s encephalopathy, hematoma, hypersensitivity pneumonitis, hypertriglyceridemia, hypothalamic hypopituitarism, idiopathic normal-pressure hydrocephalus, inflammatory pseudotumor, mesenteric fibromatosis, milk protein allergy, myotonic dystrophy, nonbacterial osteitis, organic dust toxic syndrome, panniculitis, POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes), polymer fume fever, post–cardiac injury syndrome, primary biliary cirrhosis, primary hyperparathyroidism, pulmonary embolism, pyoderma gangrenosum, retroperitoneal fibrosis, sclerosing mesenteritis, subacute thyroiditis (de Quervain’s), Sweet syndrome (acute febrile neutrophilic dermatosis), thrombosis, tubulointerstitial nephritis and uveitis syndrome (TINU), ulcerative colitis

Thermoregulatory Disorders

• Central:
  Brain tumor, cerebrovascular accident, encephalitis, hypothalamic dysfunction
• Peripheral:
  Exercise-induced hyperthermia, hyperthyroidism, pheochromocytoma