Pyrexia of unknown origin

Question 1

Definition

Answer 1

Temperature of more than 38° on several occaisions, illness of more than 3 weeks duration and unclear reason after 1 week of hospitalisation

Question 2

Mechanisms of fever

Answer 2

Exogenous pyrogens (bacteria, toxins) → activate macrophages → produce cytokines (IL-1, TNFalpha, IFNgamma) → IL-6 → Hypothalamus → prostaglandin production (mediate febrile response) plus feedback on cytokine expression

Question 3

Bacterial causes

Answer 3

Abscess
Infective endocarditis
TB
Osteomyelitis
Biliary system infection
UTI

Question 4

Parasites

Answer 4

Malaria
Amoebic liver disease
Toxoplasmosis
Tryparisomiasis
Leischmaniasis
Babesciosis

Question 5

Malignancy

Answer 5

Hodgkin's
Non-Hodgkin's
Leukaemia
Renal cell carcinoma
Hepatocarcinoma
Atrial myxomas

Question 6

Granulomatous disease

Answer 6

Sarcoidosis
IBD
Temporal arteritis
Hepatitis

Question 7

Autoimmune/connective tissue

Answer 7

SLE
Adult onset still's disease
PMR
Hypersensitivity/idiopathic vasculitis
Polyarteritis nodosa
Erythema multiform
Mixed connective tissue disease
Serum sickness
Rheumatic fever

Question 8

Other

Answer 8

Drugs: abx, phenytoin, allopurinol, quinidine
Factitious
Rare: familial Mediterranean fever, porphyrias, endocrine

Question 9

Investigations

Answer 9

Repeated hx and examination
Multiple blood cultures (different sites/times)
Imaging
FNA/biopsy (lymph node, bronchial, liver, bone)
Laparoscopy
Barium studies
Tuburculine/IFNgamma