FEVER IN UNKNOWN ORIGIN

This refers to fever of more than 3 weeks duration, the cause of which is still unknown in spite of at least 1 week of intensive investigations. Assessment of such a patient should include observation of the fever pattern, detailed history
and physical examination, laboratory tests, and non-invasive and invasive procedures.

This definition excludes common conditions of shorter duration and/ or where the cause of the fever has already been determined within 3 weeks.

COMMON CONDITIONS MANIFESTING AS FEVER OF UNKNOWN ORIGIN

Most cases of prolonged obscure fever are due to well known diseases. Aggressive diagnostic effort is recommended as most of them are treatable. Do not just shift from one antibiotic to another as this confuses the picture even
more. It may be better to stop every treatment and watch for a few days.

1. INFECTIONS

  • Tuberculosis: This is the commonest cause of pyrexia of unknown origin . Miliary tuberculosis may not be visible on chest x-ray until the disease is well advanced. Tuberculosis in other body sites like the central nervous
    system or abdominal lesion may be difficult to diagnose early.
  • Infections due to some bacterial infections, without distinctive localizing signs, such as salmonellosis and brucellosis.
  • Deep seated bacterial: Abscesses like intracranial, intra-abdominal, and hepatic abscesses may present as fever of unknown origin.
  • Infective endocarditis.
  • Some slow viruses, the commonest of which is HIV.
  • Visceral leishmaniasis.

2. NEOPLASMS

Lymphomas are the commonest among the neoplastic causes of PUO. Diagnosis may be difficult if lesions are deep seated retroperitoneal nodes.

3. IMMUNOLOGICAL DISORDERS

These include:

  • Juvenile rheumatoid arthritis and
  • Systemic lupus erythematosus.

Investigations

Routine investigations as set out under these immunological disorders, including a chest x-ray. In difficult cases it is worthwhile to consider the following:

  • Repeated history taking and examination may detect new clinical features that give a clue or old clinical signs previously missed or overlooked.
  • New tests can include:
    • Immunological: Rheumatoid factor (Rh factor), antinuclear antibody (ANA)
    • Ultrasound
    • Computerized axial tomography (CT) scans
    • Echocardiography
    • Specific according to suspected diagnosis
    • Bone marrow aspirate cytology and culture
    • Very rarely invasive procedure, e.g., laparatomy

Management

  • Treat all diagnosed conditions in accordance with the diagnosis.
  • Refer or consult if:
    • Patient deteriorates rapidly.
    • Tests described above are not available in your centre.
    • Invasive procedure that needs more skill is required.