A 6-month-old boy is brought to the emergency department due to poor feeding, irritability, and rash. He was well-appearing until 2 days ago, when he developed little interest in drinking and a progressive rash. Physical examination reveals diffuse erythema and desquamation that is most prominent at the neck, axillae, inguinal folds, and perioral region. The perioral area also has crusting and the lips are dry and cracked, but the mucosal membranes are normal. The epidermis easily comes off with gentle pressure at the erythematous areas. Which of the following is the most likely cause of this patient's symptoms?

Question

A 6-month-old boy is brought to the emergency department due to poor feeding, irritability, and rash.  He was well-appearing until 2 days ago, when he developed little interest in drinking and a progressive rash.  Physical examination reveals diffuse erythema and desquamation that is most prominent at the neck, axillae, inguinal folds, and perioral region.  The perioral area also has crusting and the lips are dry and cracked, but the mucosal membranes are normal.  The epidermis easily comes off with gentle pressure at the erythematous areas.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_37ee_c9f9_9249_77ef8060da1c_MD0001_00 This patient's fever and desquamating rash are most consistent with staphylococcal scalded skin syndrome (SSSS), an infection caused by strains of exotoxin-producing Staphylococcus aureus. Exfoliative exotoxins act as proteases that cleave desmoglein in desmosomes, which are junctions that adhere epidermal cells together. Skin damage occurs as the exotoxins spread, causing separation of keratinocytes and superficial epidermal blistering. Gentle pressure causes detachment and shedding of the outer layer of skin (ie, Nikolsky sign). The rash, although diffusely erythematous and painful ("scalded"), is most prominent in the skin folds (eg, neck, axillae, groin). Perioral involvement (eg, erythema, crusting) is common, but the mucous membranes are spared. SSSS is most common in infants and young children, and skin findings are often preceded or accompanied by fever, irritability, malaise, and poor feeding. Treatment includes antistaphylococcal antibiotics (eg, nafcillin, oxacillin). (Choice A) Pemphigus vulgaris is caused by an autoantibody to desmoglein and results in a positive Nikolsky sign and epidermal erosions, blisters, and bullae. This disorder is uncommon in children, and mucous membranes are almost always involved. (Choice B) Cell-mediated (ie, type IV delayed-type) hypersensitivity, in which sensitized T_H1 cells secrete cytokines to attract cytotoxic T cells and NK cells, is responsible for Stevens-Johnson syndrome and toxic epidermal necrolysis. Blistering, bullae, and Nikolsky sign may be seen, but mucosal involvement is almost always present. In addition, a preceding trigger (eg, medication, Mycoplasma pneumoniae infection) would be expected. (Choice C) Lipopolysaccharides (ie, endotoxin) released into the blood by gram-negative bacteria can cause a severe, widespread inflammatory response (septic shock). Purpuric lesions may occur with gram-negative sepsis, but Nikolsky sign would not be present. (Choice E) Crosslinking of IgE on the cell surface causes mast cell degranulation that is associated with allergic reactions. Urticaria (hives) appears as itchy, erythematous, blanching papules, not diffuse erythema or desquamation. Educational objective: Staphylococcal scalded skin syndrome occurs in infants and children due to the production of exfoliative exotoxins by Staphylococcus aureus. The toxins cleave desmoglein in desmosomes, leading to widespread epidermal blistering and shedding, especially with gentle pressure (ie, Nikolsky sign). Mucous membranes are spared. __________ References: Staphylococcal scalded skin syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/28846262)

A 6-Month-Old Boy Is Brought to the Emergency Department Due