Worldwide, infection is the leading cause of<unk>  with prevalence varying by country and geographic region. Extrapulmonary tuberculosis is the most frequent cause of<unk> . Drug-induced hyperthermia, as the sole symptom of an adverse drug reaction, should always be considered. Disseminated granulomatoses such as tuberculosis, histoplasmosis, coccidioidomycosis, blastomycosis and sarcoidosis are associated with<unk> . Lymphomas are the most common cause of<unk>  in adults. Thromboembolic disease (i.e. pulmonary embolism, deep venous thrombosis) occasionally shows fever. Although infrequent, its potentially lethal consequences warrant evaluation of this cause. Endocarditis, although uncommon, is another important etiology to consider. Bartonella infections are also known to cause<unk> . Human herpes viruses are a common cause of<unk>  with one study showing Cytomegalovirus, Epstein-Barr Virus, human herpesvirus 6 (HHV-6), human herpesvirus 7 (HHV-7) being present in 15%, 10%, 14% and 4.8% respectively with 10% of people presenting with co-infection (infection with 2 or more human herpes viruses). Infectious mononucleosis, most commonly caused by EBV, may present as a<unk> . Other symptoms of infectious mononucleosis vary with age with middle aged adults and the elderly more likely to have a longer duration of fever and leukopenia, and younger adults and adolescents more likely to have splenomegaly, pharyngitis and lymphadenopathy. Endemic mycoses such as histoplasmosis, blastomycosis, coccidiomycosis and paracoccidioidomycosis can cause a<unk>  in immunocompromised as well as immunocompetent persons. These endemic mycoses may also present with pulmonary symptoms or extra-pulmonary symptoms such as B symptoms (such as fevers, chills, night sweats, unexplained weight loss). The endemic mycotic infection talaromycosis primarily affects those who are immunocompromised. Invasive opportunistic mycoses may also occur in immunocompromised people; these include aspergillosis, mucormycosis, Cryptococcus neoformans. Cancer can also cause<unk> . This is thought to be due to release of pyrogenic cytokines from cancer cells as well as due to spontaneous tumor necrosis (sometimes with secondary infections). The cancer types most associated with<unk>  include renal cell carcinoma, lymphoma, liver cancer, ovarian cancer atrial myxoma and Castleman disease. In those with HIV currently being treated with antiretroviral therapy and with a low or undetectable viral load; causes of<unk>  are usually not associated with HIV infection. But in those with AIDS, with high viral loads, viral replication and immune-compromise; cancers and opportunistic infection are the most common cause of<unk> . Approximately 2 weeks after initial HIV infection, with viral loads being high, an acute retroviral syndrome can present with fevers, rash and mono-like symptoms. Immune reconstitution inflammatory syndrome is a common cause of<unk>  when a previously suppressed immune system is re-activated. The newly active immune system often has an exaggerated response against opportunistic pathogens leading to a fever and other inflammatory symptoms. Immune reconstitution syndrome commonly presents as after microbiological control of infection (in cases of immune suppressing pathogens such as HIV) but the syndrome may also present after organ transplant, in the post-partum state, with formerly neutropenic hosts or withdrawing anti-TNF therapy. Auto-inflammatory and auto-immune disorders account for approximately 5-32% of<unk> . These can be classified as purely auto-inflammatory disorders (disorders of innate immunity, with dysregulated interleukin 1 beta and/or IL-18 responses), purely auto-immune disorders (in which the adaptive immunity is dysregulated, with a dysregulated type 1 interferon response) or disorders with mixed features. Rheumatoid arthritis or Adult-onset Still's disease have mixed features and are common causes of<unk> . Here are the known causes of<unk> . Infection Infection cause Localized pyogenic infections * Appendicitis * Cat-scratch disease * Cholangitis * Cholecystitis * Dental abscess * Diverticulitis/abscess * Lesser sac abscess * Liver abscess * Mesenteric lymphadenitis * Osteomyelitis * Pancreatic abscess * Pelvic inflammatory disease * Perinephric/intrarenal abscess * Prostatic abscess * Renal malakoplakia * Sinusitis * Subphrenic abscess * Suppurative Thrombophlebitis * Tubo-ovarian abscess Intravascular infections * Bacterial aortitis * Bacterial endocarditis * Vascular catheter infection Systemic bacterial infections * Bartonellosis * Brucellosis * Campylobacter infection * Cat-scratch disease/bacillary angiomatosis (B. henselae) * Gonococcemia * Legionnaires' disease * Leptospirosis * Listeriosis * Lyme disease * Melioidosis * Meningococcemia * Rat-bite fever * Relapsing fever * Salmonellosis * Syphilis * Tularemia * Typhoid fever * Vibriosis * Yersinia infection Mycobacterial infections * M. avium/M. intracellulare infections * Other atypical mycobacterial infections * Tuberculosis Other bacterial infections * Actinomycosis * Bacillary angiomatosis * Nocardiosis * Whipple's disease Rickettsial infections * Anaplasmosis * Ehrlichiosis * Murine typhus * Q fever * Rickettsialpox * Rocky Mountain spotted fever * Scrub typhus Chlamydial infections * Lymphogranuloma venereum * Psittacosis * TWAR (C. pneumoniae) infection Viral infections * Chikungunya fever * Colorado tick fever * Coxsackie B virus infection * Cytomegalovirus infection * Dengue * Epstein-Barr virus infection * Hepatitis A, B, C, D, and E * HIV infection * Human herpesvirus 6 infection * Lymphocytic choriomeningitis * Parvovirus B19 infection * Picornavirus Fungal infections * Aspergillosis * Blastomycosis * Candidiasis * Coccidioidomycosis * Cryptococcosis * Histoplasmosis * Mucormycosis * Paracoccidioidomycosis * Pneumocystis pneumonia * Sporotrichosis Parasitic infections * Amebiasis * Babesiosis * Chagas' disease * Leishmaniasis * Malaria * Strongyloidiasis * Toxocariasis * Toxoplasmosis * Trichinellosis Neoplasm Although most neoplasms can present with fever, malignant lymphoma is by far the most common diagnosis of<unk>  among the neoplasms. In some cases the fever even precedes lymphadenopathy detectable by physical examination. Neoplasm cause Disease name Hematologic malignancies * Amyloidosis * Immunoblastic T-cell lymphoma * Castleman's disease * Hodgkin's lymphoma * 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 * Colon cancer * Renal cell carcinoma * Pancreatic cancer * Hepatoma * Sarcoma * Gall bladder carcinoma * Most of solid tumors and metastases can cause fever. Benign * Atrial myxoma * Renal Angiomyolipoma * Cavernous hemangioma of the liver * Craniopharyngioma * Necrosis of dermoid tumor in Gardner syndrome Noninfectious inflammatory diseases Noninfectious inflammatory diseases Disease name Systemic rheumatic and autoimmune diseases * Ankylosing spondylitis * Antiphospholipid syndrome * Autoimmune Hemolytic anemia * Autoimmune Hepatitis * Behçet's disease * Cryoglobulinemia * Dermatomyositis * Felty syndrome * Gout * Mixed connective tissue disease * Polymyositis * Pseudogout * Reactive arthritis * Relapsing polychondritis * Rheumatic fever * Rheumatoid arthritis * Sjögren's syndrome * Systemic lupus erythematosus * Vogt–Koyanagi–Harada disease Vasculitis * Allergic vasculitis * Eosinophilic granulomatosis with polyangiitis (Churg–Strauss syndrome) * Giant-cell arteritis/polymyalgia rheumatica * Granulomatosis with polyangiitis * Kawasaki disease * Hypersensitivity vasculitis * Polyarteritis nodosa * Takayasu's arteritis * Urticarial vasculitis Granulomatous diseases * Granulomatous hepatitis * Sarcoidosis * Midline granuloma Autoinflammatorysyndromes * Adult-onset Still's disease * Blau syndrome * CAPS (Cryopyrin-associated periodic syndrome) * Crohn's disease * DIRA (Deficiency of the interleukin-1–receptor antagonist) * Erythema multiforme * Erythema nodosum * Hemophagocytic syndrome * Hypersensitivity pneumonitis * Juvenile idiopathic arthritis * PAPA syndrome (pyogenic sterile arthritis, pyoderma gangrenosum, and acne) * PFAPA syndrome: periodic fever, adenitis, pharyngitis, aphthae * Recurrent idiopathic Pericarditis * SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteomyelitis) * Schnitzler syndrome * Takayasu's arteritis * Weber–Christian disease Miscellaneous conditions * ADEM (acute disseminated encephalomyelitis) * Adrenal insufficiency * Aneurysm * Anomalous thoracic duct * Aortic dissection * Aortic-enteral fistula * Aseptic meningitis (Mollaret’s syndrome) * Atrial myxoma * Brewer’s yeast ingestion * Caroli disease * Cholesterol emboli * Complex partial status epilepticus * Cyclic neutropenia * Drug fever * Erdheim–Chester disease * Extrinsic allergic alveolitis * Factitious disease * Fire-eater’s lung * Fraudulent fever * Gaucher’s disease * Hamman–Rich syndrome (acute interstitial pneumonia) * Hashimoto’s encephalopathy * Hematomas * Hemoglobinopathies * Hypersensitivity pneumonitis * Hypertriglyceridemia * Hypothalamic hypopituitarism * Idiopathic normal-pressure hydrocephalus * Inflammatory pseudotumor * Kikuchi’s disease * Linear IgA dermatosis * Laennec's cirrhosis * Mesenteric fibromatosis * Metal fume fever * 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 * Postmyocardial infarction syndrome * Primary biliary cirrhosis * Primary hyperparathyroidism * Recurrent pulmonary emboli * Pyoderma gangrenosum * Retroperitoneal fibrosis * Rosai-Dorfman disease * Sclerosing mesenteritis * Silicone embolization * Subacute thyroiditis (de Quervain's) * Sweet syndrome (acute febrile neutrophilic dermatosis) * Thrombosis * Tubulointerstitial nephritis and uveitis syndrome (TINU) * Tissue infarction/necrosis * Ulcerative colitis Inherited and metabolic diseases * Adrenal insufficiency * Cyclic neutropenia * Deafness, urticaria, and amyloidosis * Fabry disease * Familial cold urticaria * Familial Mediterranean fever * Hyperimmunoglobulinemia D and periodic fever * Muckle–Wells syndrome * Tumor necrosis factor receptor–associated periodic syndrome (familial Hibernian fever) * Type V Hypertriglyceridemia Thermoregulatory disorders Thermoregulatory disorders Location Central * Brain tumor * Cerebrovascular accident * Encephalitis * Hypothalamic dysfunction Peripheral * Anhidrotic ectodermal dysplasia * Exercise-induced hyperthermia * Hyperthyroidism * Pheochromocytoma Habitual hyperthermia * Exaggerated circadian rhythm Other * “Afebrile”<unk>  <38.3 °C (100.94 °F)
Fever of unknown origin
Q fever
Relapsing fever
Pontiac fever
Enterotoxemia
Cat Scratch Fever
Morning sickness
Streptococcal pharyngitis