Triggers of fever can be various diseases such as:
- Infections (> 50 %) such as infectious diseases, tuberculosis, bacterial endocarditis, pyelonephritis (Herold 2022)
- Autoimmune diseases (approx. 15 %) such as vasculitides and collagenoses (Herold 2022)
- Malignancies (approx. 7 %) such as renal cell carcinoma, Hodgkin's/ non- Hodgkin's lymphomas, tumors of the gastrointestinal tract (Herold 2022)
- Drug Reaction with Eosinophilia and Systemic Symptom(DRESS):
This is a fever triggered by drugs. Drug fever can be caused by allopurinol and antiepileptic drugs. In this case, the fever occurs about 3 - 4 weeks after the start of medication (Herold 2022).
DRESS can be triggered by carbamazepine and phenytoin in particular. After onset of DRESS, reactivation of viral infections may occur several weeks later (Herold 2022).
- Postinfarction fever:
Before the time of coronary intervention, postinfarction fever occurred in 25-50% of patients. It remains unclear whether infarct size correlates with the level of body temperature. According to a 2007 study by Naito et al, a temperature elevation of ≥ 38 degrees C poses an increased risk of, for example, aneurysm formation, decreased left ventricular pump function, and re-hospitalization due to heart failure (Smid 2018).
- Postoperative fever:
Post-aggregation metabolism may cause an increase in temperature postoperatively. Normally, normalization occurs on day 2-3. If there are temperature increases over this period, especially if accompanied by leukocytosis, a workup should be performed immediately (Schumpelik 2010), as the fever may then be caused by wound infections, nosocomial pneumonias, urinary tract infections (through bladder catheters), deep vein thrombosis, or thromboembolism (Herold 2022).
- Other causes such as hyperthyroidism, etc.
- Fever of unclear et iology (Herold 2022):
Fever of unknown origin (FUO) is defined as multiple temperatures of ≥ 38.2 degrees C that persist for 2 to 3 weeks, the cause of which cannot be determined despite one week of intensive investigation according to Petersdorf and Beeson (1961). In the meantime, a revised version speaks of:
- Nosocomial FUO:
The causes of classic fever of unknown origin (FUO) are approximately:
- 25 % by infections
- 10 - 15 % by malignancies
- 40 % by autoimmunopathies, collagenoses or others
- 20 - 25 % ultimately remain unexplained (Weihrauch 2022)
In hospitalized patients, infected intravascular catheters, urinary tract infections, pneumonia, sinusitis, pulmonary embolism, deep vein thrombosis, or reactivation of a herpes simplex infection or cytomegalovirus infection can be particularly common (Herold 2022).
- FUO in neutropenic patients:
In this case, during or after cytostatic therapy, the number of neutrophil granulocytes is between 500 - 1,000 / µl. This is found in up to 75% of patients. In about 50 % the cause remains unclear. Even in these unexplained cases, one should suspect an infection. Most commonly, germs such as staphylococci, streptococci, gram-negative bacteria or fungi are the trigger (Herold 2022).
- FUO without neutropenia:
This is often found in abscesses, endocarditis , HIV- infection, opportunistic infections, and tuberculosis (Herold 2022).
- HIV-associated FUO:
Once CD4- lymphocytes are < 200 / µl, opportunistic infections may occur such as mycobacteria, P. jirovecii, etc (Herold 2022).