This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
Erythema multiforme is most commonly caused by? 
Select and explain. 
A. Herpes simplex, B. Idiopathic, C. TB, D. Drugs
B: Idiopathic
Answer: B: Idiopathic 
Explanation: Ans. is 'b' i.e., Idiopathic Idiopathic erythema multiforme is the most common cause of EM. Herpes simplex is the most impoant infectious cause of EM. Causes of Erythema multiforme Idiopathic --) Most common cause Viral --> HSV (most impoant) HBV, Mumps, Adenovirus Bacteria - Streptococci, tuberculosis Fungal --> Coccidioidomycosis, Histoplasmosis. Drugs ---> Antibiotics (Sulphonamide), Phenytoin, NSAIDS. Autoimmune disease --> SLE, thyroiditis, RA Others --> Sarcoidosis, Pregnancy, Malignancy.