Fever of unknown origin (FUO) 원인불명열 – Dr. John Sangwon Lee's Pediatric Updates

Fever of unknown origin (FUO)

원인불명열

Definition of unexplained fever

oral_tem_s.jpg Photo 8-6.

Take your temperature to see if you have a fever.

Copyright ⓒ 2011 John Sangwon Lee, MD, FAAP

A fever of unknown cause is known as fever when the fever continues to occur in children for 8 days or longer, and in adults for 3 weeks or longer, but the obvious cause of the fever is not found by examination findings and the first clinical examination.
It is also defined as an unknown fever or an unknown fever),
A fever of at least 38.3°C (101°F) or higher in 14 days lasting for at least 4 hours, and at least 4 or more times of that fever is sometimes defined as an unexplained fever.
sauce; Emergency Pediatrics, A guide to ambulatory care, 5th edi. Roger M. Barkin, Peter Rosen, p.245
It is also defined differently.
Causes of unexplained fever
Fever is diagnosed as unexplained fever when a fever continues for 3 weeks or more in adults and 8 days or more in children, but the cause of fever is not found even after diligently searching for the cause.
Fever when the cause of the fever is found in the hospital for 7 days and the cause is not found is sometimes diagnosed as a fever of unknown cause.
When It looks for the cause of the fever for more than 3 weeks outside the hospital, it is called an unknown fever when I cannot find the cause of the fever.
fever-unknown-origin-1s.jpg Figure 37.
If the fever persists for 8 days or more (for children), or continues for 3 weeks or longer (for adults) without being able to clearly determine the cause of the fever from the first examination findings and clinical examination.
In this case, it can be defined as a fever of unknown cause.
Vol. 21 Children and Adolescents Home ∙ School Nursing References and Sources-11.
Diagnosis of fever of unknown origin If the fever continues for 8 to 2 weeks, and the cause of the fever is not clearly found even after the past medical history, family history, current medical history, symptoms, signs, examination findings, etc.
are synthesized and appropriate clinical tests are performed, it is called an unknown fever.
These unexplained columns are defined in several ways.
Tuberculosis, other infectious diseases, cancer, leukemia, A fever can be caused by a urinary tract infection.
Even if you repeat appropriate examinations and clinical tests to find out why you have a fever when you have such a disease, you may not be able to make a diagnosis for the first time.
Infected with Salmonella from pet turtles or snakes and contracted Salmonella infectious disease,
After eating poorly managed melon or watermelon,
you can become infected with Salmonella and get a Salmonella infectious disease.
When suffering from these infectious diseases,the diagnosis may not be made for the first few days, and the diagnosis may be made with unexplained fever.
Malaria, which is only prevalent in that region when traveling to a certain region or country,
Rocky Mountain spotted fever Q
You can get a fever for more than 8 days due to a specific infectious disease in a specific area, such as fever.
Some people are diagnosed with unexplained fever because they do not know whether they have such a disease and have not been able to make a diagnosis for the first time.
After eating raw milk, you can get Brucellosis disease and have a fever for more than 8 days.
After eating uncooked food, you can get infectious diseases such as larval organ transfer syndrome and intestinal sputum,
and you may continue to have a fever for more than 8 days.
Twenty percent of unexplained fevers can go away spontaneously without knowing the cause of the fever, even if you try to find the cause of the fever.
80% of unexplained fevers in children and adolescents are caused by infectious diseases or diseases such as:

Viral (sex) infectious disease
Brucella disease
Jagjit adverb
Tularemia
Appendicitis and resulting abscess
osteomyelitis
Combustion rheumatoid arthritis
Inflammatory enteritis
malignant tumor
Meningitis that is not completely cured
Kawasaki disease
Cat scratch disease
endocarditis
urinary tract infection
Other Treatment of unexplained fever If you have a fever and get sick a lot, you should be admitted to the hospital and have repeated checkups to diagnose.
Sometimes the appropriate clinical tests also need to be repeated several times.
Sometimes, parents may complain that their child has a fever even though they don’t actually get a fever when they take the child’s temperature incorrectly, read the temperature incorrectly, or take a fever with the wrong thermometer.
If their child doesn’t actually have a fever, but your child has a fever, you can misdiagnose it as a fever of unknown cause.
The type of fever you have all day, or for a week or two during that time, is helpful in diagnosing the disease that causes the fever.
That’s why parents need to measure and record the heat at home.
If you feel like your child has a fever for a long time, you should check your child temperature first to see if your child really had a fever.
After being admitted to the hospital, you can find out more about your your child past and present medical history, measure your child’s body temperature directly by a nurse, etc., and repeat medical examinations several times to diagnose an unexplained fever.
CBC blood test, erythrocyte sedimentation rate (ESR) test, antinuclear antibody (ANA), C-reactive protein, Anti-streptolysin O level test (ASO level/Streptolysin), urine chemistry test and urine bacterial culture test, liver function test, chest X-ray, other types of a blood test, blood, cerebrospinal fluid, urine, feces, etc.
By doing a bacterial culture test and a tuberculin skin reaction test to find out if there is tuberculosis, you can diagnose which tuberculosis infectious disease or other diseases other than the infectious disease cause fever in any part of the body.
Sometimes, some of these clinical tests are repeated several times.
If you suspect rheumatoid fever or juvenile rheumatoid arthritis, Erythrocyte sedimentation rate/ESR test, Antinuclear Antibody/ANA test, C-reactive protein, Test for antistreptolysin O (ASO) titer, etc.
Antinuclear antibody tests and rheumatoid factor tests are valuable for diagnosing juvenile rheumatoid arthritis, and antinuclear antibody tests are useful for diagnosing systemic lupus erythematosus.
Diagnosing unexplained fever like this really requires a lot of pediatric science.
An unexplained fever is a challenging clinical problem, so it can be evaluated by a good doctor if properly handled.
In general, symptoms can be treated with antipyretic analgesics or anti-inflammatory drugs such as aspirin, acetaminophen (Tylenol under the trade name Acetaminophen), or “Ibuprofen” until the disease-causing fever of unknown cause is clearly diagnosed.
As long as you don’t.
If the result of the urine chemistry test and urine bacterial culture test is abnormal when there is a fever of unknown cause, use a renal ureter, bladder ultrasound, etc. to determine whether there is posterior urethral valve obstruction, bladder ureter reflux, kidney disease, or urinary tract infection.
If appendicitis, peritonitis, or an abscess in the abdominal cavity are suspected, an intraperitoneal CT scan can be done.
You may get a fever due to vasculitis caused by Kawasaki disease.
In that case, it is diagnosed by performing an appropriate test.
If the CBC blood test is abnormal and you have a fever or leukemia is suspected, a bone marrow puncture and a bone marrow bacterial culture may be performed.
Other rare diseases, such as fungal intrathoracic lymphadenitis, pneumonia, sarcoidosis, and histoplasmosis, may cause unexplained fever.
It can be diagnosed based on suspicion and by performing appropriate tests.
[Parents should also be at least a half-doctor’s Encyclopedia of Child and Family Nursing]-Vol. 7 Pediatric Infectious Diseases-See column of unknown cause urinalysis_chemical_s.jpg Photo 38.
If necessary, a urine chemistry test and a urine bacterial culture test are also performed.
Copyright ⓒ 2011 John Sangwon Lee, MD., FAAP bacterial_culture_and_sensitivity_test-2s.jpg
Figure 39. Bacterial culture tests are also performed with urine, blood, feces, cerebrospinal fluid, etc. as needed.
Sometimes repeated tests.

Copyright ⓒ 2011 John Sangwon Lee, MD, FAAP

Copyright drleepediatrics.com 2/16/2026

원인불명열

원인불명열의 정의
사진 8-6.
체온을 측정하여 열이 있는지 확인하십시오.
저작권 ⓒ 2011 John Sangwon Lee, MD, FAAP
원인불명열이란 소아의 경우 8일 이상, 성인의 경우 3주 이상 열이 지속되지만, 진찰 소견 및 초기 임상 검사에서 명확한 원인을 찾을 수 없는 경우를 말합니다.
(원인불명열은 미상열 또는 원인불명열이라고도 합니다.)
14일 동안 38.3°C(101°F) 이상의 열이 4시간 이상 지속되고, 이러한 열이 4회 이상 발생하는 경우를 원인불명열이라고 정의하기도 합니다.
출처: 응급소아과, 외래 진료 안내서, 5판 로저 M. 바킨, 피터 로젠, 245쪽
또한 다른 정의가 있습니다.
원인 불명의 발열의 원인
성인의 경우 3주 이상, 소아의 경우 8일 이상 발열이 지속되지만, 원인을 찾기 위해 부지런히 노력했음에도 불구하고 발열의 원인을 찾을 수 없을 때 원인 불명의 발열로 진단합니다.
병원에서 7일 동안 발열의 원인을 찾았음에도 원인을 찾지 못한 경우에도 원인 불명의 발열로 진단하는 경우가 있습니다.
병원 밖에서 3주 이상 발열의 원인을 찾으려고 노력했지만 원인을 찾지 못한 경우를 원인 불명의 발열이라고 합니다.
그림 37.
소아의 경우 8일 이상, 성인의 경우 3주 이상 발열이 지속되지만, 최초 진찰 소견 및 임상 검사에서 발열의 원인을 명확히 파악할 수 없는 경우
원인 불명의 발열로 정의할 수 있습니다.
Vol. 21. 아동 및 청소년 가정·학교 간호 참고자료 및 출처-11.
원인 불명의 발열 진단: 발열이 8주에서 2주 동안 지속되고, 과거 병력, 가족력, 현재 병력, 증상, 징후, 신체검사 소견 등을 종합하고 적절한 임상 검사를 시행했음에도 발열의 원인이 명확하게 밝혀지지 않는 경우를 원인 불명의 발열이라고 합니다.
이러한 원인 불명의 발열은 여러 가지로 정의됩니다.
결핵, 기타 감염성 질환, 암, 백혈병, 요로 감염 등이 발열의 원인이 될 수 있습니다.
이러한 질환이 있는 경우, 발열의 원인을 찾기 위해 적절한 검사와 임상 검사를 반복하더라도 처음에는 진단이 내려지지 않을 수 있습니다.
애완용 거북이나 뱀으로부터 살모넬라균에 감염되어 살모넬라 감염성 질환에 걸린 경우,
관리가 제대로 되지 않은 멜론이나 수박을 섭취한 후,
살모넬라균에 감염되어 살모넬라 감염성 질환에 걸릴 수 있습니다.

이러한 전염병에 걸렸을 때,

처음 며칠 동안은 진단이 내려지지 않을 수 있으며, 원인을 알 수 없는 발열로 진단될 수도 있습니다.
말라리아는 특정 지역이나 국가로 여행할 때 해당 지역에서만 유행합니다.
록키산 반점열
특정 지역에서 발생하는 특정 감염성 질환으로 인해 8일 이상 열이 지속될 수 있습니다.
어떤 사람들은 자신이 그러한 질병에 걸렸는지 알지 못하고 처음에는 진단을 받지 못했기 때문에 원인을 알 수 없는 발열로 진단받습니다.
생우유를 섭취하면 브루셀라증에 걸려 8일 이상 열이 날 수 있습니다.
익히지 않은 음식을 섭취하면 유충 장기 전이 증후군이나 장내 가래와 같은 감염성 질환에 걸릴 수 있으며,
8일 이상 열이 지속될 수 있습니다.
원인을 알 수 없는 발열의 20%는 발열의 원인을 찾으려고 노력하더라도 원인을 알 수 없이 저절로 사라집니다.

소아 및 청소년의 원인 불명 발열의 80%는 감염성 질환 또는 다음과 같은 질환으로 인해 발생합니다.
바이러스성(성병) 감염
브루셀라병
야자열
툴라레미아
맹장염 및 그로 인한 농양
골수염
화농성 류마티스 관절염
염증성 장염
악성 종양
완치되지 않은 뇌수막염
가와사키병
고양이 할큄병
심내막염
요로 감염
원인 불명 발열의 기타 치료법 열이 나고 자주 아프다면 입원하여 정확한 진단을 위해 반복적인 검진을 받아야 합니다.

때때로 적절한 임상 검사를 여러 번 반복해야 할 수도 있습니다.
간혹 부모가 아이의 체온을 잘못 재거나, 잘못 읽거나, 잘못된 체온계를 사용하여 실제로 열이 없는데도 열이 있다고 호소하는 경우가 있습니다.

만약 상대 아이의 아이가 실제로 열이 없는데, 당신의 아이에게 열이 있다면, 원인을 알 수 없는 열로 오진할 수 있습니다.
하루 종일 또는 1~2주 동안 지속되는 열의 양상은 열을 유발하는 질병을 진단하는 데 도움이 됩니다.
그렇기 때문에 부모는 집에서 아이의 열을 측정하고 기록해야 합니다.
아이가 오랫동안 열이 있는 것 같으면, 먼저 아이의 체온을 측정하여 실제로 열이 있는지 확인해야 합니다.
병원에 입원한 후에는 아이의 과거 및 현재 병력을 자세히 알아보고, 간호사에게 직접 체온을 측정받는 등 여러 차례 진찰을 반복하여 원인 불명의 열을 진단할 수 있습니다.

혈액검사(CBC), 적혈구침강속도(ESR) 검사, 항핵항체(ANA), C-반응성 단백질, 항스트렙토라이신 O 수치 검사(ASO 수치/스트렙토라이신), 소변 화학 검사 및 소변 세균 배양 검사, 간 기능 검사, 흉부 X선 검사, 기타 혈액 검사, 혈액, 뇌척수액, 소변, 대변 검사 등이 있습니다.
세균 배양 검사와 투베르쿨린 피부 반응 검사를 통해 결핵 여부를 확인하고, 신체의 어느 부위에서든 발열을 유발하는 감염성 질환이 결핵인지 아니면 다른 질환인지 진단할 수 있습니다.
때때로 이러한 임상 검사 중 일부는 여러 번 반복됩니다.

류마티스열이나 소아 류마티스 관절염이 의심되는 경우, 적혈구 침강 속도(ESR) 검사, 항핵항체(ANA) 검사, C-반응성 단백질(CRP) 검사, 항스트렙토라이신 O(ASO) 역가 검사 등을 시행할 수 있습니다.
항핵항체 검사와 류마티스 인자 검사는 소아 류마티스 관절염 진단에 유용하며, 항핵항체 검사는 전신성 루푸스 진단에도 도움이 됩니다.
이처럼 원인을 알 수 없는 발열을 진단하려면 소아과 의학에 대한 상당한 지식이 필요합니다.
원인 불명의 발열은 까다로운 임상 문제이므로, 숙련된 의사가 적절히 대처한다면 진단이 가능합니다.

일반적으로 원인 불명의 발열은 아스피린, 아세트아미노펜(타이레놀, 상품명 아세트아미노펜), 이부프로펜과 같은 해열 진통제나 항염증제로 증상을 완화할 수 있으며, 질병의 원인이 명확히 진단될 때까지 복용합니다.

원인 불명의 발열이 있는 경우, 소변 화학 검사 및 소변 세균 배양 검사 결과가 비정상이면 신장 요관 초음파, 방광 초음파 등을 시행하여 후부 요도 판막 폐쇄, 방광 요관 역류, 신장 질환 또는 요로 감염 여부를 확인해야 합니다.
맹장염, 복막염 또는 복강 내 농양이 의심되는 경우, 복강 내 CT 촬영을 시행할 수 있습니다.
가와사키병으로 인한 혈관염 때문에 발열이 발생할 수도 있습니다.

이 경우, 적절한 검사를 통해 진단합니다.

CBC 혈액 검사 결과가 비정상이고 열이 있거나 백혈병이 의심되는 경우, 골수 천자 및 골수 세균 배양 검사를 시행할 수 있습니다.
곰팡이성 흉강 내 림프절염, 폐렴, 사르코이드증, 히스토플라스마증과 같은 드문 질환도 원인 불명의 발열을 유발할 수 있습니다.
진단은 의심을 바탕으로 적절한 검사를 시행하여 내릴 수 있습니다.

[부모는 최소한 소아 및 가족 간호 백과사전 제7권 소아 감염 질환 편(원인 불명 소변 화학 검사 항목, 사진 38 참조)에 대한 지식을 갖추어야 합니다.] 필요한 경우 소변 화학 검사 및 소변 세균 배양 검사도 시행합니다.

저작권 ⓒ 2011 John Sangwon Lee, MD., FAAP bacterial_culture_and_sensitivity_test-2s.jpg
그림 39. 필요에 따라 소변, 혈액, 대변, 뇌척수액 등에서도 세균 배양 검사를 시행합니다.
때로는 반복 검사가 필요합니다.
저작권 ⓒ 2011 John Sangwon Lee, MD, FAAP
저작권 drleepediatrics.com 2026년 2월 16일

Fever of unknown origin (FUO)

원인불명열

Definition of unexplained fever

oral_tem_s.jpg Photo 8-6.

Take your temperature to see if you have a fever.

Copyright ⓒ 2011 John Sangwon Lee, MD, FAAP

A fever of unknown cause is known as fever when the fever continues to occur in children for 8 days or longer, and in adults for 3 weeks or longer, but the obvious cause of the fever is not found by examination findings and the first clinical examination.

It is also defined as an unknown fever or an unknown fever),

A fever of at least 38.3°C (101°F) or higher in 14 days lasting for at least 4 hours, and at least 4 or more times of that fever is sometimes defined as an unexplained fever.

sauce; Emergency Pediatrics, A guide to ambulatory care, 5th edi. Roger M. Barkin, Peter Rosen, p.245

It is also defined differently.

Causes of unexplained fever

Fever is diagnosed as unexplained fever when a fever continues for 3 weeks or more in adults and 8 days or more in children, but the cause of fever is not found even after diligently searching for the cause.

Fever when the cause of the fever is found in the hospital for 7 days and the cause is not found is sometimes diagnosed as a fever of unknown cause.

When It looks for the cause of the fever for more than 3 weeks outside the hospital, it is called an unknown fever when I cannot find the cause of the fever.

fever-unknown-origin-1s.jpg Figure 37.

If the fever persists for 8 days or more (for children), or continues for 3 weeks or longer (for adults) without being able to clearly determine the cause of the fever from the first examination findings and clinical examination.

In this case, it can be defined as a fever of unknown cause.

Vol. 21 Children and Adolescents Home ∙ School Nursing References and Sources-11.

Diagnosis of fever of unknown origin If the fever continues for 8 to 2 weeks, and the cause of the fever is not clearly found even after the past medical history, family history, current medical history, symptoms, signs, examination findings, etc.

are synthesized and appropriate clinical tests are performed, it is called an unknown fever.

These unexplained columns are defined in several ways.

Tuberculosis, other infectious diseases, cancer, leukemia, A fever can be caused by a urinary tract infection.

Even if you repeat appropriate examinations and clinical tests to find out why you have a fever when you have such a disease, you may not be able to make a diagnosis for the first time.

Infected with Salmonella from pet turtles or snakes and contracted Salmonella infectious disease,

After eating poorly managed melon or watermelon,

you can become infected with Salmonella and get a Salmonella infectious disease.

When suffering from these infectious diseases,the diagnosis may not be made for the first few days, and the diagnosis may be made with unexplained fever.

Malaria, which is only prevalent in that region when traveling to a certain region or country,

Rocky Mountain spotted fever Q

You can get a fever for more than 8 days due to a specific infectious disease in a specific area, such as fever.

Some people are diagnosed with unexplained fever because they do not know whether they have such a disease and have not been able to make a diagnosis for the first time.

After eating raw milk, you can get Brucellosis disease and have a fever for more than 8 days.

After eating uncooked food, you can get infectious diseases such as larval organ transfer syndrome and intestinal sputum,

and you may continue to have a fever for more than 8 days.

Twenty percent of unexplained fevers can go away spontaneously without knowing the cause of the fever, even if you try to find the cause of the fever.

80% of unexplained fevers in children and adolescents are caused by infectious diseases or diseases such as:

Viral (sex) infectious disease

Brucella disease

Jagjit adverb

Tularemia

Appendicitis and resulting abscess

osteomyelitis

Combustion rheumatoid arthritis

Inflammatory enteritis

malignant tumor

Meningitis that is not completely cured

Kawasaki disease

Cat scratch disease

endocarditis

urinary tract infection

Other Treatment of unexplained fever If you have a fever and get sick a lot, you should be admitted to the hospital and have repeated checkups to diagnose.

Sometimes the appropriate clinical tests also need to be repeated several times.

Sometimes, parents may complain that their child has a fever even though they don’t actually get a fever when they take the child’s temperature incorrectly, read the temperature incorrectly, or take a fever with the wrong thermometer.

If their child doesn’t actually have a fever, but your child has a fever, you can misdiagnose it as a fever of unknown cause.

The type of fever you have all day, or for a week or two during that time, is helpful in diagnosing the disease that causes the fever.

That’s why parents need to measure and record the heat at home.

If you feel like your child has a fever for a long time, you should check your child temperature first to see if your child really had a fever.

After being admitted to the hospital, you can find out more about your your child past and present medical history, measure your child’s body temperature directly by a nurse, etc., and repeat medical examinations several times to diagnose an unexplained fever.

By doing a bacterial culture test and a tuberculin skin reaction test to find out if there is tuberculosis, you can diagnose which tuberculosis infectious disease or other diseases other than the infectious disease cause fever in any part of the body.

Sometimes, some of these clinical tests are repeated several times.

If you suspect rheumatoid fever or juvenile rheumatoid arthritis, Erythrocyte sedimentation rate/ESR test, Antinuclear Antibody/ANA test, C-reactive protein, Test for antistreptolysin O (ASO) titer, etc.

Antinuclear antibody tests and rheumatoid factor tests are valuable for diagnosing juvenile rheumatoid arthritis, and antinuclear antibody tests are useful for diagnosing systemic lupus erythematosus.

Diagnosing unexplained fever like this really requires a lot of pediatric science.

An unexplained fever is a challenging clinical problem, so it can be evaluated by a good doctor if properly handled.

In general, symptoms can be treated with antipyretic analgesics or anti-inflammatory drugs such as aspirin, acetaminophen (Tylenol under the trade name Acetaminophen), or “Ibuprofen” until the disease-causing fever of unknown cause is clearly diagnosed.

As long as you don’t.

If appendicitis, peritonitis, or an abscess in the abdominal cavity are suspected, an intraperitoneal CT scan can be done.

You may get a fever due to vasculitis caused by Kawasaki disease.

In that case, it is diagnosed by performing an appropriate test.

If the CBC blood test is abnormal and you have a fever or leukemia is suspected, a bone marrow puncture and a bone marrow bacterial culture may be performed.

Other rare diseases, such as fungal intrathoracic lymphadenitis, pneumonia, sarcoidosis, and histoplasmosis, may cause unexplained fever.

It can be diagnosed based on suspicion and by performing appropriate tests.

[Parents should also be at least a half-doctor’s Encyclopedia of Child and Family Nursing]-Vol. 7 Pediatric Infectious Diseases-See column of unknown cause urinalysis_chemical_s.jpg Photo 38.

If necessary, a urine chemistry test and a urine bacterial culture test are also performed.

Copyright ⓒ 2011 John Sangwon Lee, MD., FAAP bacterial_culture_and_sensitivity_test-2s.jpg

Figure 39. Bacterial culture tests are also performed with urine, blood, feces, cerebrospinal fluid, etc. as needed.

Sometimes repeated tests.

Copyright ⓒ 2011 John Sangwon Lee, MD, FAAP

Copyright drleepediatrics.com 2/16/2026