1. EM Boards Question
Susan Gutierrez

2. A 7 year old non-verbal female with autism spectrum disorder presents to the emergency department for evaluation of a rash. Her mother first noticed the skin findings today and says that one of the lesions drained clear fluid. The patient’s mother says that her daughter has been infrequently scratching the area over the past few days. She had an abrasion on the buttock 1 week prior. On examination, there are several superficial ulcerations with moist, erythematous bases on the left buttock, extending to the proximal thigh.
T 37.1 P 127 RR 28 BP 96/58 O2 99

3. The most likely diagnosis for these skin findings is:
Photo courtesy of Robert P. Blereau, MD
The most likely diagnosis for these skin findings is:

4. A Pemphigus vulgaris
B Herpes simplex infection
C Scabies
D Bullous impetigo
E Dermatitis herpetiformis

5. Correct answer: D. Bullous impetigo
This patient’s presentation is consistent with the diagnosis of bullous impetigo. Bullous impetigo is caused by strains of staphylococcus aureus that produce exfoliative toxin A, a toxin that targets the desmoglein protein, resulting in the loss of cell adhesion in the superficial epidermis. There is a high risk of spread of the bullous impetigo via auto-inoculation, and patients may present with primary lesions surrounded by satellite lesions, as shown in this photograph. Appropriate topical treatments for bullous impetigo include mupirocin and retapamulin. For bullous impetigo with multiple lesions, as seen in this photograph, oral therapy is indicated. Acceptable oral antibiotics for impetigo include dicloxacillin and cephalexin, which are effective against staph aureus and strep. Typical duration of treatment is 7 days.

6. Pemphigus vulgaris is an autoimmune blistering disorder cause by circulating antibodies to desmoglein III. Much like bullous impetigo, pemphigus vulgaris causes large, flaccid bullae to form on the skin. The initial presentation of pemphigus vulgaris is typically in the mouth, making this option less likely.
While cutaneous herpes simplex infections do occur, such as with herpes gladiatorum and herpetic whitlow, such infections are quite rare and do not cause large, ruptured bullae as shown in this photograph.

7. Scabies does not result in the formation of bullae.
Dermatitis herpetiformis is caused by IgA antibodies that are directed at epidermal transglutaminase and is a condition exclusively seen in patients with celiac disease. It presents with small, intensely pruritic papules and vesicles and can be distributed anywhere on the epidermis, typically sparing mucous membranes. DH does not present with large bullae.

8. Sources:
For further reading on bullous impetigo, refer to the following link: &search=treatment%20bullous%20impetigo&selectedTitle=1~19#H4
For further reading on pemphigus vulgaris, herpes simplex infection, scabies, and epidermolysis bullosa, refer to Nelson’s Textbook of Pediatrics 20th Edition.