What is meant by pyrexia of unknown origin? Outline 8 causes of pyrexia of unknown origin? Outline clinical approach to a case presenting with fever,rationalizing each step?

Pyrexia of unknown origin (PUO) refers to a fever of unknown cause that persists for more than three weeks despite extensive investigation. It is a challenging clinical scenario that requires a thorough evaluation to identify the underlying cause.

Causes of pyrexia of unknown origin can be broadly categorized into infectious, inflammatory, neoplastic, and miscellaneous causes. Some common causes include:

1. Infectious causes: such as tuberculosis, endocarditis, abscesses, and viral infections.
2. Inflammatory causes: such as autoimmune diseases like rheumatoid arthritis or inflammatory bowel disease.
3. Neoplastic causes: such as lymphoma, leukemia, or other malignancies.
4. Miscellaneous causes: such as drug-induced fever, factitious fever, or granulomatous diseases like sarcoidosis.

Clinical approach to a case presenting with fever:

1. History and physical examination: Obtain a detailed history including the onset, duration, and pattern of fever, as well as associated symptoms. Perform a thorough physical examination to look for any localizing signs.

2. Initial investigations: Start with basic investigations such as complete blood count, inflammatory markers (CRP, ESR), blood cultures, and imaging studies like chest X-ray.

3. Further investigations: Depending on initial findings, further investigations may include serological tests for specific infections, autoimmune markers, imaging studies (CT scan, MRI), and tissue biopsy if indicated.

4. Empirical treatment: Initiate empirical treatment if a specific cause is suspected based on initial investigations, while awaiting further test results.

5. Re-evaluation: If the fever persists despite initial investigations and treatment, reassess the patient's history and physical examination, and consider a multidisciplinary approach involving specialists from different fields.

6. Specialized investigations: Consider specialized tests such as PET scan, bone marrow biopsy, or genetic testing if initial investigations are inconclusive.

7. Consultation: Seek input from infectious disease specialists, rheumatologists, oncologists, or other specialists as needed to help in the diagnostic workup.

8. Follow-up: Monitor the patient closely, and continue to investigate and treat based on the evolving clinical picture until a definitive diagnosis is reached.

Overall, a systematic and thorough approach is essential in evaluating a case of pyrexia of unknown origin to identify the underlying cause and provide appropriate treatment.

Pyrexia of Unknown Origin (PUO)

Pyrexia of unknown origin refers to a fever that persists for at least 3 weeks, with an unknown cause despite extensive medical evaluation.

Causes of Pyrexia of Unknown Origin

1. Infections (e.g., endocarditis, tuberculosis, fungal infections)
2. Neoplastic diseases (e.g., lymphoma, leukemia)
3. Inflammatory diseases (e.g., connective tissue disorders, autoimmune disorders)
4. Drugs (e.g., antibiotics, anticonvulsants)
5. Granulomatous diseases (e.g., sarcoidosis, eosinophilic granuloma)
6. Malignant hyperthermia
7. Endocrine disorders (e.g., Addison's disease)
8. Psychological factors (e.g., factitious fever)

Clinical Approach to Fever

Step 1: Initial History and Physical Examination

- Obtain a detailed medical history (including recent travel, exposures, medications, and past illnesses)
- Perform a thorough physical examination to identify any potential source of infection or inflammation

Step 2: Investigations

- Blood tests: Complete blood count, blood cultures, liver function tests, renal function tests, inflammatory markers (e.g., C-reactive protein, erythrocyte sedimentation rate)
- Imaging studies: Chest X-ray, computed tomography scan (CT), magnetic resonance imaging (MRI)
- Microbiological testing: Stool cultures, urine cultures, sputum cultures, serological testing for infectious diseases

Step 3: Ruling Out Common Causes

- Consider potential infections, such as pneumonia, urinary tract infection, and tuberculosis
- Evaluate for drug reactions, endocrinopathies, and malignancies

Step 4: In-depth Investigations

- If common causes are ruled out, consider less common causes, such as granulomatous diseases, autoimmune disorders, and factitious fever
- Consult with specialists (e.g., infectious disease, oncology, immunology)
- Perform more specialized tests (e.g., bone marrow biopsy, lymph node biopsy)

Step 5: Management

- Treat any identified underlying condition
- Provide symptomatic treatment to reduce fever and discomfort
- Follow-up closely to monitor response to treatment and identify any complications