DDx of an Erythematous Rash with Nikolsky Sign and Fever

Staphylococcal Scalded Skin Syndrome:Known as Ritter disease or dermatitis exfoliativa neonatorum, staphylococcal SSS presents as a scarlatiniform, erythematous rash that blisters and sloughs (positive Nikolsky sign). Children younger than 5 years are at highest risk.
Patients initially have an abrupt fever, erythema of the neck, axillae, and groin, and extreme skin tenderness. Diagnostic clues include a lack of mucous membrane involvement and a skin cleavage plane that is more shallow than that associated with TEN.
Treatment of this infection includes antistaphylococcal antibiotics, fluid and electrolyte management, and local wound care. Young, well-appearing patients with minimal skin sloughing may be managed as outpatients. In young children, this disease has a mortality of less than 5%; in contrast, this disease is very rare in adults, but when it occurs, mortality can be as high as 60%.
Toxic Epidermal Necrolysis (Adults): TEN, also known as Lyell disease, is the most serious cutaneous drug reaction and most commonly associated with sulfa drugs. Other important triggers include anticonvulsants, antivirals, NSAIDs, and allopurinol.
TEN presents as sudden-onset diffuse erythema with tender skin and sloughing. Symptoms occur first on the face and around the eyes, spread caudally to the shoulders and upper extremities, and then progress to the whole body. The skin cleavage is full thickness (positive Nikolsky sign and Asboe-Hansen sign - a blister that spreads into clinically normal skin with light lateral pressure), with massive skin sloughing in large sheets. Patients with TEN are toxic, with myalgias and substantial mucous membrane involvement. The mortality of TEN is considerable—30% to 35% with optimal care.
At-risk populations include those with head injuries, brain tumors, systemic lupus erythematosus (SLE), and immunocompromise. Importantly, HIV patients have a TEN risk that is 1,000 times greater than that in patients without HIV.
Treatment consists of discontinuation of the offending agent, wound care, eye care, and fluid and electrolyte resuscitation. Intravenous immune globulin (IVIG) may be helpful, although it is not yet FDA approved for this indication. Most physicians recommend against steroid use. Sulfadiazine should not be used on the wounds, as sulfa is the most common offending agent. Patients with TEN usually require ICU admission and should be managed in a burn unit if skin sloughing is extensive.