A 4-year-old girl is brought to the emergency department due to blisters on her left hand. Two days ago, the patient developed small, fluid-filled lesions, which have since increased in size and are now mildly tender and itchy. She has a history of eczema and takes no medications. Temperature is 38.1 C (100.6 F). Vital signs are otherwise normal. Examination findings of the hand are shown in the image below. Which of the following is the most likely pathogen of this patient's condition?

Question

A 4-year-old girl is brought to the emergency department due to blisters on her left hand.  Two days ago, the patient developed small, fluid-filled lesions, which have since increased in size and are now mildly tender and itchy.  She has a history of eczema and takes no medications.  Temperature is 38.1 C (100.6 F).  Vital signs are otherwise normal.  Examination findings of the hand are shown in the image below.  Which of the following is the most likely pathogen of this patient's condition?

Quizplus · Accepted Answer

11ec25c8_d64c_3cfe_bc81_a7c997ae62a7_MD0003_00 This patient has localized bullae with yellow fluid and crusting overlying sites of ruptured bullae, which are findings consistent with bullous impetigo. Impetigo is a superficial bacterial infection of the epidermis typically caused by bacterial invasion through a break in the skin barrier (eg, wound, eczema, burn). Bullous impetigo is caused by Staphylococcus aureus, which produces an exfoliative toxin that disrupts cell adhesion in the superficial skin layers. bullous impetigo Bullous impetigo presents with enlarging vesicles, which progress into flaccid bullae filled with yellow fluid. The lesions rupture, leaving a classic collarette of scale (eg, resembles a collar or necklace) at the periphery of the lesion. Ruptured lesions may develop an overlying crusting, although they often lack the classic honey-colored coating of nonbullous impetigo. Lesions may be tender and/or pruritic. Patients may also have a fever. Diagnosis is clinical, and treatment of bullous impetigo is with oral antibiotics (eg, cephalexin). Lesions typically resolve without scarring or long-term sequelae. (Choice A) Hand-foot-and-mouth disease is caused by coxsackie virus. It typically presents with oral lesions in addition to a bilateral, nontender, nonpruritic maculopapular and/or vesicular rash of the palms and soles. Hand-foot-and-mouth disease is unlikely in a child with isolated, unilateral findings. Hand-foot-and-mouth disease (Choice B) Herpes simplex virus infection presents with clusters of painful vesicles classically occurring at the vermilion border of the lips but can develop on the fingers (eg, herpetic whitlow) or hands. In contrast to this patient, lesions do not enlarge rapidly or leave a collarette of scale during resolution. lips (Choice C) Sporotrichosis caused by Sporothrix schenckii causes draining, nodular ulcerations (not bullae) most commonly along the lymphatic chain that drains at the initial site of inoculation. Sporotrichosis (Choice E) Nonbullous impetigo can be caused by S aureus (most common) or Streptococcus pyogenes, both of which cause papules and pustules that coalesce and rupture, leaving a thick, adherent, honey-colored crusting. In contrast, bullous impetigo is exclusively caused by S aureus. Nonbullous impetigo (Choice F) Shingles occurs most commonly in adults and is caused by varicella zoster virus. It presents with painful vesicles and bullae in a dermatomal distribution. This patient's age and lack of significant pain make this diagnosis unlikely. Shingles Educational objective: Bullous impetigo presents with enlarging, yellow fluid-filled, flaccid bullae that leave a collarette of scale after rupture. This condition is caused by Staphylococcus aureus, and treatment is with oral antibiotics. References: Impetigo: diagnosis and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/25250996) Impetigo. (http://www.ncbi.nlm.nih.gov/pubmed/28613693)

A 4-Year-Old Girl Is Brought to the Emergency Department Due