A 5-year-old girl is brought to the clinic due to a rash. The patient developed multiple pruritic lesions over her neck and left arm 2 weeks ago. Similar lesions have also developed on the patient's cousin who recently spent the night, and the family is concerned about some form of infestation. The family searched their home including furniture and found numerous webs. Vital signs are normal. On examination, the patient is scratching her neck and left arm where multiple 3- to 5-mm erythematous papules are arranged in a linear pattern. Several of the papules have a central hemorrhagic punctum. Which of the following is the most likely diagnosis in this patient?

Question

A 5-year-old girl is brought to the clinic due to a rash.  The patient developed multiple pruritic lesions over her neck and left arm 2 weeks ago.  Similar lesions have also developed on the patient's cousin who recently spent the night, and the family is concerned about some form of infestation.  The family searched their home including furniture and found numerous webs.  Vital signs are normal.  On examination, the patient is scratching her neck and left arm where multiple 3- to 5-mm erythematous papules are arranged in a linear pattern.  Several of the papules have a central hemorrhagic punctum.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d647_f735_bc81_4f6198ab8dcd_MD0003_00 Small, pruritic, erythematous papules in a linear pattern are suggestive of bedbug bites. Bedbugs are small, red-brown, blood-feeding insects that hide in clusters within the surrounding environment (eg, folds of mattress, cushions) and feed at night. Transmission occurs within a physical living space or via colonized objects (eg, luggage); person-to-person transmission is rare. Bites are typically painless and located on exposed areas (eg, neck, arms). The local inflammatory reaction causes 2- to 5-mm pruritic, erythematous papules. A characteristic appearance of clustered, linear lesions is often described as a "breakfast, lunch, and dinner" pattern, presumably from bedbugs searching for superficial vessels to feed. Salivary proteins of the bedbug can inhibit coagulation; bites often present with a central hemorrhagic punctum, as seen in this patient. Household contacts with similar symptoms support the diagnosis, but confirmation requires visualization of bedbugs. Treatment of the patient is supportive (eg, topical corticosteroids, oral antihistamines) because bites and local reactions resolve within a week. However, bedbugs can live for up to a year without feeding. Therefore, definitive treatment requires eradication of bedbugs, such as insecticides and high heat. Contaminated objects can be frozen or laundered on high heat as well. (Choice B) Chiggers are small mites that cause intensely pruritic, erythematous papules on exposed areas (eg, ankles, waistline). However, a linear pattern is not characteristic. In addition, chiggers are found outdoors (eg, grassy fields), making this diagnosis less likely in a patient with a symptomatic household contact. (Choice C) Pediculosis capitis causes scalp pruritus due to infestation of live lice, which are often visible on examination. (Choice D) Scabies is a contagious mite infestation that causes intensely pruritic, erythematous papules, which may have hemorrhagic crusting and nearby burrows (fine, serpiginous lines). In contrast to this patient, the affected areas are typically intertriginous (eg, web spaces, axillae, buttocks). (Choices E and F) A spider bite typically occurs as an isolated papule or pustule with localized inflammation. A tick bite usually causes an isolated, asymptomatic or pruritic, erythematous papule. This patient's multiple lesions make these diagnoses unlikely. Educational objective: Bedbug bites present as small, pruritic, erythematous papules, often arranged in a linear pattern on exposed areas and each with a central hemorrhagic punctum. Management of bites is supportive, but definitive treatment requires eradication of the bugs. References: Bedbug bites. (http://www.ncbi.nlm.nih.gov/pubmed/30844155)

A 5-Year-Old Girl Is Brought to the Clinic Due to a Rash