The document discusses pyrexia of unknown origin (PUO), defined as fever over 38.3°C on at least two occasions with an illness duration exceeding three weeks, and outlines the diagnostic workup including various tests and examinations. Common causes include infections, malignancies, and autoimmune disorders, with specific attention to the diagnostic approach in immunocompromised patients. Urgent considerations for conditions like temporal arteritis and giant cell arteritis are highlighted, emphasizing the need for empirical antibiotic treatment and corticosteroids to prevent serious complications.

1. Pyrexia of
Unknown Origin
- Dr. Akif A.B

2. -Fever >38.3*C (101*F) on atleast 2 occasions
- illness duration more than 3 weeks
-No known immunocompromised state
-Uncertain diagnosis despite one week of inpatient evaluation

3. Uncertain diagnosis despite one week of
inpatient evaluation Should include:
History and clinical examination
Complete blood count
Liver function test
Renal function test
Chest x ray
Ultrasound abdomen
ANA, CK, Ferritin, RA factor
Protein electrophoresis
Blood and urine cultures
- If all these tests doesn’t lead a doctor to a diagnosis, then it is
labelled as PUO

4. ETIOLOGY
1) Infections - most common
2) Malignancy
3) Autoimmune/ Connective tissue disorders
4) Other causes
In up to 20% of cases, cause of fever will not be identified despite
thorough workup
Temporal arteritis accounts for 16-17% of all causes of FUO in
the elderly

6. INFECTIONS
-Most common infectious causes are:
Tuberculosis
Intrabdominal and pelvic Abscesses
-FUO in immunocompromised patients is often very difficult to diagnose
-Previously HIV was one of the most common cause but now its been
routinely tested

7. The most common malignancies are Hodgkin disease and
non-Hodgkin lymphoma.
MALIGNANCY
Diagnosis of malignancy or autoimmune disorders becomes
more likely as the duration of the fever increases.

8. Urgent Considerations
In PUO
Immunocompromised patients Giant cell arteritis suspect
Should be empirically treated
with broad spectrum
antibiotics till the time we get
a specific diagnosis
Should be treated with
Corticosteroids since if not
treated early may lead to
blindness.

9. Work up

10. - PDCs : Potentially Diagnostic Clues (Symptoms, signs and clues directing
toward one diagnosis)

12. History
Past medical history
Known malignancy (recent chemotherapy, recent neutrophil count)
Previously treated diseases such as endocarditis, tuberculosis, rheumatic
fever
Comorbid conditions (eg. diabetes)
Past surgical history
Type and date of surgery performed
Postoperative complications
Any indwelling foreign material
A history of calf swelling, pain, or redness is suggestive of DVT.

13. Medication history
Full list of medications
Include over-the-counter and herbal remedies
Social history
Recent travel history
Sexual history including enquiring about sexual practices
Recreational drug use
Hobbies including exposure to pets/animals
Employment history including exposures
Unusual dietary habits eg. consumption of unpasteurised
dairy products or rare meats
History

14. Skin and nail bed exam for clubbing, nodules, lesions, rashes
Temporal artery palpation
Gums and oral cavity
Auscultation for bruits and murmurs
Abdominal palpation for hepatosplenomegaly
Rectal examination for abscesses
Testicular examination
Palpate for lymphadenopathy
Focal neurologic signs
Musculoskeletal: bony tenderness, joint effusion
Examination

15. Differential Diagnosis
Common Uncommon
Tuberculosis All rest causes
Abdominal and pelvic
abscesses
HIV
Sinusitis: Acute or chronic
Thyroiditis

16. References:
1) Harrison’s 19th edition
2) PUO, BMJ

17. Tuberculosis