Pyrexia of unknown origin – Causes, symptoms and treatment

Pyrexia of unknown origin is the condition when a fever greater than 101 degrees F persists for longer than three weeks without a specific cause.

Fever of unknown origin, also known as pyrexia of unknown origin (PUO) is defined as continuous or intermittent fever of 101 degrees F and above, lasting for more than three weeks, even after extensive tests are carried out, including one week of hospital stay.

The normal temperature of individuals varies between 97 and 99 degrees Fahreinheit. Pyrexia of unknown origin is said to have occurred when a person’s temperature is lower in the morning and highest during late afternoon and evening.

Types of pyrexia of unknown origin

Classic PUO – Examples: Infection, malignancy and collagen vascular disease.
Nosocomial PUO (hospital acquired infections) – Examples: Clostridium difficile enterocolitis and septic thrombophlebitis.
Immune deficient PUO – Examples: Opportunistic bacterial infections and occult fungal infections.
HIV associated infections PUO – Examples: Cytomegalovirus infection and pneumonia by pneumocystis carinii

Causes pyrexia of unknown origin

About 25% of PUO are due to infections, which could be bacterial, viral, parasitic, fungal or mixed.
Some may be due to a cancer (leukemia, lymphomas and brain tumour) or non-inflammatory conditions.
Patients whose immune system is suppressed due to HIV or medicines have a higher chance of contracting PUO than the normal population.
Drugs like antibiotics (penicillin, sulphonamidesand anti-tubercular drugs) or those used to lower blood pressure or control seizures can cause fever as a side-effect.
Vaccines given as a part of immunization may cause fever.
Extreme exhaustion, excessive workouts causing dehydration and prolonged exposure to the sun may resemble fever.
Systemic disorders like juvenile rheumatoid arthritis and systemic lupus erythematosus are other causes.
Abdominal causes of fever are pancreatitis, inflammatory bowel disease, liver disease, cholecystitis.
Specific infections like tuberculosis, typhoid, endocarditis, osteomyelitis and septicaemia are possible causes.
An abscess anywhere in the body if not drained can cause a fever for e.g. lung, brain, intra-abdominal and pelvic abscesses.

Symptoms of pyrexia of unknown origin

A person could be suffering from continuous or intermittent fever, above 101 degrees Fahreinheit lasting for more than three weeks without a diagnosis.

Another symptom could be fever of 101 degrees Fahreinheit or more for three weeks or more, including extensive investigations for at least a week in hospital.

Other symptoms could be cough, loose stools, vomiting depending on the illness.

Children may have seizures if the temperature goes very high. These are called febrile convulsions and must be evaluated by a doctor.

Diagnosis of pyrexia of unknown origin

The doctor will take note of your medical history and ask if you have recently had surgery, travelled to a new place where you may have picked up an infection, taken any medications lately for another illness and details of the fever, whether continuous, intermittent or associated with chills or rigors.

Even after the person has been diagnosed with PUO, the doctor should make an attempt to find out the cause instead of just treating the patient after conducting the routine tests.

Investigations to diagnose pyrexia of unknown origin

Blood tests include CBC, ESR, Widal test for typhoid fever, tests for HIV and hepatitis B or A, peripheral smear for malarial parasites, blood culture, liver function tests, tests for syphilis, Q fever, amoebiasis, brucellosis.
Skin tests like tuberculin test, sweat test for e.g.in diabetes insipidus, there is an absence of sweating.
Imaging tests like abdominal ultrasound, echocardiogram, CT scan, plain and contrast X rays and in some cases MRI may be helpful.
Biopsy of a certain region like liver or bone marrow or a lumbar puncture in cases of brain pathology can be done, if above tests are inconclusive and suspicion is towards that particular organ.
Endoscopy may be done if bowel involvement is suspected.
A new tool called positron emission tomography or PET is useful in ruling out inflammatory causes of PUO.

Treatment of pyrexia of unknown origin

Some doctors may avoid giving antibiotics or other medicines blindly till a diagnosis is made. Nearly 50 percent of PUO cases remain undiagnosed and are blamed on viruses.

Treatment is individualised, depending on factors like if the patient is diabetic, or suffering from liver disease or is HIV positive.

Photograph via sxc.hu

You may also like:

Pyrexia of unknown origin – Causes, symptoms and treatment is a post from: mDhil