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Pyrexia of Unknown Origin Module

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TopicPyrexia of Unknown Origin
AuthorBeatrice Zanetti
DurationUp to 2 hours
Equipment requiredNone
  • Basics (10 mins)
  • Main session: (2 x 15 minute) case discussions covering the key points and evidence
  • Advanced session: (2 x 20 minutes) case discussions covering grey areas, diagnostic dilemmas; advanced management and escalation
  • Quiz (10 mins)
  • Infographic sharing (5 mins): 5 take home learning points

We also recommend printing/sharing a copy of your local guideline.

To prepare for this session, learners could read the below case report article (20 minutes): 

Wood M, Abinun M. and Foster H., Pyrexia of unknown origin. Archives of Disease in Childhood, Education and Practice, 89 ep 63-69 (2004) 

And/or look at these useful resources from the web: 

https://pedemmorsels.com/fever-of-unknown-origin/ (5 minutes)

https://dontforgetthebubbles.com/recurrent-or-periodic-fevers-investigate-or-reassure/ (10 minutes)

https://dontforgetthebubbles.com/tuberculosis/ (5 minutes)

https://dontforgetthebubbles.com/claire-nourse-tuberculosis-at-dftb17/ (20 minutes)

https://gppaedstips.blogspot.com/search/label/Juvenile%20idiopathic%20arthritis  (10 minutes)

https://www.paediatricfoam.com/?s=kawasaki (10 minutes)

The term pyrexia of unknown origin (PUO) is used when a patient has more than 8 days with fever (temperature> 38°C) without a clinical diagnosis after exhaustive investigations have been carried out (in hospital or in primary care). 

Other more specific PUOs are:

  • nosocomial PUO
  • neutropenic PUO
  • HIV-associated PUO

These 3 have specific risk factors and will not be covered in this session. 

Fever is a sign of an underlying pathology. In PUO, pyrexia is usually the main symptom while other signs may be very subtle. Many times, the underlying disease is a common pathology that is presenting in an atypical or incomplete way.  

Here are 3 main clinical dilemmas for clinicians: 

How can we discern a benign illness from a life-threatening condition?

How far should we investigate?

Should we treat empirically or have a wait-and-see approach? 

A 14-month-old girl was referred to hospital by GP due to 8 days of fever, non-tender cervical lymphadenopathies (scattered small submandibular, posterior and 1 supraclavicular lymphadenopathies) and mild cough. On examination, the patient has a good general appearance with a mildly red throat and the above described lymphadenopathies. Father is concerned as the child also had a febrile illness the previous week which was labelled as a viral infection. 

Blood tests showed raised WCC (24×109/L) with neutrophilia (18×109/L). Normal lymphocytes (6 x109/L) with a CRP of 30 mg/L. Chest x-ray showed a bilateral bronchial opacification.

The patient was admitted and started on amoxicillin and azithromycin PO. 

Despite 5 days of treatment, the patient is still spiking fevers (see chart below). Blood culture is negative. Clinically stable, cough has now disappeared. You are classifying this patient as PUO. 


What questions do you want to ask the parents? Take a detailed history. 

Why is this patient not getting better despite treatment? 

What investigations can be prompted by clinical findings?

At this point, would you escalate the antibiotic treatment?

What questions do you want to ask the parents? Take a detailed history.

Why is this patient not getting better despite treatment?

What investigations can be prompted by clinical findings?

At this point, would you escalate the antibiotic treatment?

After 18 days of intermittent fever, cervical lymphadenopathies and some fatigue, the patient underwent a fine-needle aspiration of the supraclavicular lymphadenopathy. The histology showed a caseating granuloma and the microbiology sample showed acid fast bacilli. TB GeneXpert of the sample and culture were positive for non-resistant Mycobacterium Tuberculosis. Patient was diagnosed with tuberculous cervical lymphadenitis (extrapulmonary TB).

When to do a biopsy or FNA of a lymph-node?

To note, the patient had received the BCG vaccine. However, it has about 50% efficacy which implies that patients with BCG vaccination can still have tuberculosis. BCG is more effective in preventing children from developing disseminated (Miliary) TB or TB meningitis. She was probably exposed to TB and became infected while in India, subsequently developing the disease over the next few months. 

Contact tracing of family members is mandatory to identify the source case. Usually, children are not very infectious since the majority of cases tend to be paucibacillary (low bacterial load) unless they have lung cavities or extensive lung involvement. 

TB in children often presents in a non-specific way. The typical symptoms are weight loss or failure to gain weight, fever, night sweats and fatigue. When children present with pulmonary TB, this is usually confined within the intrathoracic nodes. Patients may have persistent cough and asymmetrical and persistent wheeze caused by airway compression due to enlarged tuberculous peri-hilar nodes. 

Chest XR can be helpful in the diagnosis of early primary infection by detecting intrathoracic lymph-node enlargement. However, these changes may be subtle as a strong index of suspicion is required. More information on radiological features of paediatric TB can be found on the following link: doi: 10.1101/cshperspect.a017855

Sputum and gastric aspirate mycobacterial cultures have a low diagnostic yield since most children have paucibacillary TB. Recently, diagnostic sensibility for these samples has increased due to the rollout of new molecular techniques (GeneXpert TB PCR).

TST (Mantoux test) and new immunological assays such as IGRAs detect exposure. TST is performed by injecting 0.1ml of tuberculin purified protein derivative (PPD) intradermally into the inner surface of the forearm. The skin reaction produced by the PPD should be read between 48 and 72 hours. The reaction is measured in millimetres of induration, not redness. There are different measures to define a positive result depending on patient background history (for example BCG vaccination) and there are also many causes of false positive and false negative results.For more information (https://www.cdc.gov/tb/publications/factsheets/testing/skintesting.htm).

On the other hand, IGRA is a blood test which measures the body’s immune response (interferon-gamma production) to TB antigens. Our patient had a positive Mantoux test (10 mm) but the result might have been affected by previous BCG vaccination.  However, this result, combined with a positive IGRA, demonstrated that the child had been previously exposed to TB. Unfortunately, neither of these tests can distinguish between latent infection and active disease. 

The patient was treated with Isoniazid (with Pyridoxine), Rifampicin, Ethambutol, and Pyrazinamide for 2 months and Rifampicin and isoniazid for another 4 months. Corticosteroids were not deemed necessary in this case since the lymphadenopathies were not compressing other structures. Empirical treatment of tuberculosis is usually limited to clinical cases where milliary or CNS TB are suspected, as a treatment delay in these cases will often lead to worse outcomes.

3-year-old boy with a 5-day history of fever and loss of appetite presented to the emergency department with his mother as he had been crying all night and refused to put his T-shirt on. No history of trauma reported. On examination, he looked skinny and he was crying when the right arm was moved. Bloods test showed
Hb 9 g/L
WCC 4 x109/L
Neutrophils 1.5 x109/L
Lymphocytes 2.5 x109/L
Platelets 120 x109/L.
CRP 40 mg/L.

Right arm x-ray was normal. The patient was admitted for observation. On the ward, it was noted that he was spiking fevers every night. 

After 3 days of admission, MRI of the right upper limb was performed. MRI showed possible osteomyelitis of the right distal clavicle.  He was diagnosed with acute pyogenic osteomyelitis and was started on ceftriaxone 50mg/kg IV OD. Blood cultures (taken before administration of antibiotics) were negative. Fever settled after 5 days of antibiotics. Patient was discharged home on oral antibiotics for 3 weeks.  

10 days later, the patient was reviewed in the clinic. Mother was worried since the patient had had fevers again over the last 2 days, felt fatigued and was reluctant to walk.

At this stage, what is the differential diagnosis? 

What investigations would you perform? 

What treatment would you give? If you were to suspect an autoinflammatory disease, would you give steroids? 

What is the role of PET-CT in PUO?

What is the differential diagnosis?

What investigations would you perform?

What treatment would you give? If you were to suspect an auto-inflammatory disease, would you give steroids?

What is the role of PET CT in PUO? 

4-year-old boy presented with 5 days of fever, diarrhoea and vomiting and abdominal pain. No relevant past medical history. Fully vaccinated, BCG not included.

Initial blood test showed WCC 24.5 x109/L with neutrophils of 18 x109/L. CRP 139 mg/L. Hb 110 g/L and Platelets of 395 x109/L. He was admitted and started on amoxicillin, gentamicin and metronidazole. Blood cultures were negative and urine culture showed a sterile pyuria (WCC 2250 with no growth). Stool sample was negative. Abdominal ultrasound showed free fluid in the right iliac fossa. On examination, his abdomen was soft with some tenderness in lower quadrants.  He had a second ultrasound which showed findings suggestive of an appendicular mass. A repeated urine sample had 64 WBC and no growth. 

Meanwhile, fevers persisted: on day 7, he was changed to piperacillin-tazobactam and gentamicin. He underwent a laparoscopic appendicectomy on day 8. After operation, he was afebrile for more than 48 hours and antibiotics were stopped. Histological results of the appendix were normal. On day 12 of admission, the patient started again with fever and no focus on examination.

Now that the fever has restarted, and considering the previous history, what investigations would you ask? 

Would you re-start antibiotics? 

Looking at the pattern of fever below, what can you observe? 

Would an echocardiogram help in reaching the final diagnosis?

Now that the fever has restarted, and considering the previous history, what investigations would you ask? 

Would you restart antibiotics?

Looking at the pattern of fever below, what can you observe? 

Would an echocardiogram help to reach the definitive diagnosis?

You are in an Ethiopian rural hospital. A 7-year-old boy presents to clinic severely malnourished (marasmic type). Mother is complaining of daily fevers for an unknown period of time. 

Patient has cerebral palsy due to an obstructed labour resulting in hypoxic-ischaemic injury. He was in hospital for some time after delivery. He is not vaccinated. He is on phenobarbitone 100mg OD PO for seizures. 

You admit the child to the malnutrition ward and start the appropriate treatment with F-75 Milk. Part of the SAM protocol (Severe Acute Malnutrition) includes a course of at least 7 days with Amoxicillin.  On examination, the patient has a papular rash over hands and groin compatible with scabies but no other clinical findings. On the ward, he spikes a high temperature (39°C) and he is shivering. 

Available investigations at your hospital are performed:

Blood tests: 
Hb 9.1 g/LRenal function and CRP not available in this setting.
WCC 12 x109/L with neutrophils 8 x109/L and lymphocytes 4 x109/LUrine dipstick: leucocytes and nitrates positiveUrine microscopy: many white cells. No culture available.
Platelets 300 x109/LStool: negative for parasites
Blood film: No parasites seen
GGT 61 IU/LHIV antibodies negative
GOT 72 IU/LHepatitis B and C antibodies negative
Bili < 0.5  μmol/L

Based on the above clinical picture and results, what is your differential diagnosis and management? 

Patient was empirically treated but fevers persisted. Given his background of CP and the geographical area, what other infections would you consider?

What other non-infectious causes should be considered? How can you reach the diagnoses in this low-resource-setting?

Based on the above clinical picture and results, what is your differential diagnosis and management?

Given his background of CP and the geographical area, what other infections would you consider? 

What other non-infectious causes should be considered? How can you reach the diagnoses in this low-resource-setting?

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

A roadmap for fever of unknown origin in children- Rigante, D; Esposito S., International Journal of Immunopathology and Pharmacology. Vol.26 no 2, 315-326 (2013)

Fever in Children and Fever of Unknown Origin- Rajeshwar Dayal, Dipti Agarwal, Indian Journal of Paediatrics, 83 (1): 38-43 (2016)

Pyrexia of unknown origin-Mark Wood, Mario Abinun and Helen Foster. Archives of Disease in Childhood, Education and Practice, 89 ep 63-69 (2004) 

Barbi E, Marzuillo P, Neri E, Naviglio S, Krauss BS. Fever in Children: Pearls and Pitfalls. Children (Basel). 2017;4(9):81. Published 2017 Sep 1. doi:10.3390/children4090081

Antoon J,Peritz D, Parsons M., Skinner A.,Lohr J. Etiology and resource use of fever of unknown origin in Hospitalized children. Hospital Pediatrics, 8 (3).: 135-140(2018)

For malaria: 

https://apps.who.int/iris/bitstream/handle/10665/79317/9789241548526_eng.pdf;jsessionid=AD1DDC86455A8D51D25CFEEADF7E1C75?sequence=1

Website resources: 

https://pedemmorsels.com/fever-of-unknown-origin/

https://dontforgetthebubbles.com/ent-infections-immunodeficiency/

https://dontforgetthebubbles.com/recurrent-or-periodic-fevers-investigate-or-reassure/

https://dontforgetthebubbles.com/tuberculosis/

https://dontforgetthebubbles.com/claire-nourse-tuberculosis-at-dftb17/

https://radiopaedia.org/articles/tuberculous-cervical-lymphadenitis

https://gppaedstips.blogspot.com/search/label/Juvenile%20idiopathic%20arthritis

https://www.paediatricfoam.com/?s=kawasaki

https://gppaedstips.blogspot.com/search?q=kawasaki

https://dontforgetthebubbles.com/josh-francis-rheumatic-heart-disease-at-dftb17/



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Author

  • Beatrice Zanetti was born in Italy but grew up in Spain where she studied medicine. After travelling for a bit, she is now a paediatric registrar in London with an interest in Infectious Diseases and global child health. In her spare time, she likes to crochet!

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1 thought on “Pyrexia of Unknown Origin Module”

  1. I am confused with question 3, I suspected Brucellosis which is answer c but you state it is answer B cat scratch yet go one to discuss what Brucellosis is

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