II. Causes: Infections
- Idiopathic (50%)- However, up to 90% of Erythema Multiforme Minor cases are thought due to infections
 
- 
                          Herpes Simplex Virus (>50%)- Occurs 10 days after acute eruption, and resolves over a 2 week period
- HSV may be cause even without active lesions
- Typically associated with HSV-1, but HSV-2 can also cause Erythema Multiforme
 
- 
                          Mycoplasma pneumoniae
                          - Second most common cause (esp. children)
 
- Other infections
III. Causes: Drug Sensitivity
- Background- Occurs 1-3 weeks after intake
- Highest risk with higher doses and rapid drug introduction
- Most common cause of erythema mutiforme major- Contrast with Erythema Multiforme Minor which is typically caused infections (esp. HSV, Mycoplasma)
- Medications cause 50% of Stevens Johnson
- Medications cause 90% of Toxic Epidermal Necrolysis)
 
- Most common with NSAIDS, antiepileptics and Antibiotics
 
- NSAIDs (esp. Ibuprofen)
- 
                          Antibiotics- Sulfonamides (e.g. Septra)- Trimethoprim-Sulfamethoxazole (Bactrim) is the most common cause of Erythema Multiforme Major
- Risk of Erythema Multiforme Major with Trimethoprim-Sulfamethoxazole is up to 40 fold higher in HIV
 
- Penicillins
- Erythromycin
- Nitrofurantoin
- Tetracyclines
- Ciprofloxacin
 
- Sulfonamides (e.g. Septra)
- Antiepileptics
- Vaccinations (low overall percentage risk given the very large number of annual Immunizations)
- Miscellaneous Medications- Acetaminophen
- Phenothiazines
- Bextra (FDA black box warning)
- Allopurinol
- Candesartan (Atacand)
- Metformin (Glucophage)
- TNF-alpha inhibitors (e.g. Adalimumab or Humira)
- Checkpoint Inhibitors (e.g. Pembrolizumab)
- Bupropion (Wellbutrin)
- Statins
- Corticosteroids
 
IV. Causes: Miscellaneous Causes
- Food Allergy
- Autoimmune Conditions
- Neoplasm- Associated with Leukemia, Lymphoma
- Solid organ neoplasms (Renal Cell Carcinoma, Gastric Adenocarcinoma) may cause persistent and refractory cases
- May also be associated with Radiotherapy
 
- Conditions in Women- Pregnancy
- Menstruation
 
