Corticosteroids, such as prednisone, are powerful anti-inflammatory agents used to treat a variety of conditions, including autoimmune diseases, allergies, and asthma. However, their therapeutic effects come with a significant trade-off: they suppress the immune system. This immunosuppression leaves the body vulnerable to infections. The risk and severity of these infections are directly related to the dose and duration of steroid therapy.
How Steroids Weaken the Immune System
Steroids interfere with immune cell function by blocking transcription factors that trigger inflammatory cytokines, inhibiting macrophages and T-cells, and impairing leukocyte movement. This broad effect makes the body more vulnerable to a wide range of microorganisms.
Fungal Infections
Opportunistic fungal infections, which are usually harmless, can become serious for individuals on steroids.
- Candidiasis: Candida yeast overgrowth, often in the mouth or throat, is common with systemic or inhaled steroids.
- Aspergillosis: High-dose steroids are linked to invasive aspergillosis, particularly in immunocompromised patients and those with COVID-19.
- Mucormycosis: This rare but severe fungal infection has also been associated with excessive steroid use, notably during the COVID-19 pandemic.
- Fungal Keratitis: Topical steroids can worsen fungal eye infections and delay healing.
Viral Infections
Steroids can worsen or reactivate viral infections due to a weakened immune response.
- Herpes Simplex Virus (HSV): Steroids can exacerbate cold sore outbreaks and lead to disseminated infection, so they should be avoided during flares.
- Herpes Zoster (Shingles): Reactivation of the varicella-zoster virus is a known risk of systemic steroid therapy.
- Cytomegalovirus (CMV): High-dose steroid use can increase susceptibility to CMV.
- Respiratory Viral Infections: While used for severe cases like COVID-19, high-dose steroids can delay viral clearance and increase mortality if not used appropriately.
Bacterial Infections
Common bacterial infections can become more severe, and intracellular bacteria pose a greater threat with chronic steroid use.
- Tuberculosis (TB): Corticosteroids can reactivate latent TB, and screening is recommended before immunosuppressive therapy. TB in steroid users may present atypically and have higher mortality.
- Listeria monocytogenes: Chronic steroid use increases the risk of Listeria infection.
- Salmonellosis: Salmonella infections are more frequent and potentially more severe.
- Pneumonia: Bacterial and atypical mycobacterial pneumonia are heightened risks.
Parasitic Infections
Steroids can worsen certain parasitic infections.
- Strongyloides stercoralis Hyperinfection: In individuals with latent infection, systemic steroids can trigger a life-threatening hyperinfection syndrome. Screening is important for those at risk, especially from endemic tropical areas.
- Malaria: While complex, steroids may lead to poorer outcomes in certain forms of malaria.
Comparing Steroid Therapy and Infection Risk
| Steroid Dose (Prednisone Equivalent) | Duration of Use | Risk of Serious Infection | Examples of Increased Risk Infections |
|---|---|---|---|
| Low Dose (<7.5 mg/day) | Short-term | Minimal or no increased risk | May increase risk slightly with longer term use |
| Moderate Dose (7.5-30 mg/day) | Long-term | Moderately increased risk | Herpes Zoster, Tuberculosis, Common Bacterial Infections |
| High Dose (>30 mg/day) | Short or long-term | Substantially increased risk | Opportunistic fungal infections (Aspergillosis, PJP), Disseminated Viral Infections |
Prevention Strategies
Key strategies to minimize infection risk while on steroids include:
- Dose Minimization: Use the lowest effective dose for the shortest duration.
- Prophylactic Medication: Consider prophylactic antibiotics for high-risk patients.
- Screening: Screen for latent infections like TB and Strongyloides before starting therapy.
- Vaccination: Ensure vaccinations, such as for influenza, pneumococcal pneumonia, and shingles, are current. Live vaccines are often contraindicated.
- Close Monitoring: Watch for signs of infection, noting that steroids can mask symptoms.
Conclusion
Corticosteroids, while essential for many conditions, increase the risk of infection due to immune suppression. Patients, especially those on higher doses or prolonged therapy, are more susceptible to opportunistic and common pathogens including viral, fungal, bacterial, and parasitic infections. Healthcare providers should balance benefits against infection risk, employing preventative measures like dose minimization, screening, prophylaxis, and vaccination. Patient education and close monitoring are crucial. For further information, resources are available from the National Center for Biotechnology Information.
