A 3-year-old boy is brought to the clinic by his mother for evaluation of fever and rash. He was bitten by an insect yesterday, resulting in an itchy red "bump" on his right thigh. The lesion has rapidly enlarged and become tender to the touch. The mother says, "My son awoke from his nap today with fever and chills, so I am worried that he has an infection. I rubbed a steroid medication from the drugstore on his skin, but he says it is still painful." The patient has no chronic medical conditions and takes no medications. He has no known allergies. Temperature is 39.5 C (103.1 F). Examination reveals an uncomfortable-appearing boy sitting in his mother's lap. Cardiopulmonary examination is normal. Skin examination reveals an 8-cm area of bright-red, tense, and warm skin on the right upper thigh that is well demarcated and raised relative to the surrounding, unaffected skin. No fluctuance or discharge is noted. Three tender 1.5-cm right inguinal lymph nodes are present. The remainder of the examination is unremarkable. Which of the following is the most likely diagnosis?

Question

A 3-year-old boy is brought to the clinic by his mother for evaluation of fever and rash.  He was bitten by an insect yesterday, resulting in an itchy red "bump" on his right thigh.  The lesion has rapidly enlarged and become tender to the touch.  The mother says, "My son awoke from his nap today with fever and chills, so I am worried that he has an infection.  I rubbed a steroid medication from the drugstore on his skin, but he says it is still painful."  The patient has no chronic medical conditions and takes no medications.  He has no known allergies.  Temperature is 39.5 C (103.1 F).  Examination reveals an uncomfortable-appearing boy sitting in his mother's lap.  Cardiopulmonary examination is normal.  Skin examination reveals an 8-cm area of bright-red, tense, and warm skin on the right upper thigh that is well demarcated and raised relative to the surrounding, unaffected skin.  No fluctuance or discharge is noted.  Three tender 1.5-cm right inguinal lymph nodes are present.  The remainder of the examination is unremarkable.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfc1_75b7_8f63_e50db153a5a9_MD0005_00 Erysipelas is a common, rapidly spreading, superficial bacterial infection in young children and older adults. Infection develops in a break in the skin, such as an abrasion or excoriated insect bite, and is most commonly caused by Streptococcus pyogenes, or group A Streptococcus. Physical examination shows a bright-red, well-demarcated, and raised area that is tender and tense. Typical affected areas include the ear, malar area of the face, and lower extremities. Localized lymphadenopathy and systemic symptoms (eg, fever, chills), as seen in this patient, are common. Erysipelas differs from cellulitis in its rapid onset and well-demarcated and raised appearance. Treatment is a penicillin (eg, ampicillin, amoxicillin). Erysipelas (Choice A) Abscess presents with a tender, fluctuant nodule due to a collection of pus beneath or within the dermis. Purulent drainage and fever may be present. This patient's rash is not fluctuant, and no purulent drainage is present. Abscess (Choice C) Erythema migrans is a manifestation of Lyme disease and may present as a rash with fever and localized lymphadenopathy. However, the rash is typically not tender and presents as a bull's eye lesion with central clearing. (Choice D) Impetigo is also a superficial bacterial infection but typically presents with pustules and honey-colored crusting. Systemic symptoms, such as fever and chills in this patient, are uncommon. (Choice E) Necrotizing fasciitis is also a rapidly spreading infection but classically presents with pain out of proportion to examination findings, which is not present in this patient. In addition, findings in necrotizing fasciitis can include crepitus, bullae, and ecchymoses. Educational objective: Erysipelas, most commonly caused by Streptococcus pyogenes, presents with fever and acute, rapidly spreading erythema with well-demarcated, raised borders. First-line treatment is a penicillin (eg, ampicillin, amoxicillin). References: Impetigo, erysipelas and cellulitis. (http://www.ncbi.nlm.nih.gov/pubmed/26866211)

A 3-Year-Old Boy Is Brought to the Clinic by His