<unk> -Johnoen Syndrome (SJS) and<unk><unk><unk>  (TEN) are a spectrum of disease which ultimately results in blistering and peeling of the skin
Mucous membranes can also be involved
SJS and TEN exist on a spectrum of disease
SJS involves <10% of the skin body surface area
TEN involves >30% of the skin body surface area
SJS and TEN are considered true dermatologic emergencies
SJS involves <10% of the skin body surface area
TEN involves >30% of the skin body surface area
Drugs
The most common cause overall
Many have been linked. Common offensive agents include: sulfa, quinolones, PCN, ASA, acetaminophen, carbamazepine, NSAIDs, phenytoin, corticosteroids, immunizations
High dose or rapid loading of allopurinol, lamotrigine
Malignancy - lymphoma, brain tumor treated with radiotherapy and antiepileptics
Idiopathic
Immunosuppression - HIV 
Infectious - Mycoplasma pneumoniae
Autoimmune - SLE
The most common cause overall
Many have been linked. Common offensive agents include: sulfa, quinolones, PCN, ASA, acetaminophen, carbamazepine, NSAIDs, phenytoin, corticosteroids, immunizations
High dose or rapid loading of allopurinol, lamotrigine
Stevens-Johnson syndrome and toxic epidermal necrolysis
Erythema Multiforme
Sweet's syndrome
Staphylococcal scalded skin syndrome
Poison Oak, Ivy, Sumac dermatitis
Erythroderma
Drug rash with eosinophilia and systemic symptoms syndrome
Toxic Shock Syndrome