A 3-year-old boy is brought to the clinic by his parents due to fever and a rash. Two days ago, the patient developed a fever and decreased appetite. Yesterday, a maculopapular rash appeared on his trunk and face and became vesicular. This morning, another small group of vesicles appeared on his arms and legs. The rash is intensely pruritic. The patient is playful and has been drinking normally. He is up to date on vaccinations and has no medical conditions. The patient attends day care. The family travels extensively for the mother's job, and they recently returned from a 2-week trip to South Africa. Temperature is 38.2 C (100.8 F), and pulse is 100/min. Physical examination shows a mild, diffuse maculopapular rash with some scattered, vesicular lesions on his face and hands. Examination of the mucous membranes and auscultation of the heart and lungs are normal. Which of the following is the most likely explanation for this rash?
Chickenpox (varicella) | |
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VZV = varicella-zoster virus. | |
This patient has a fever and an intensely pruritic rash that developed in successive crops and is at different stages of progression (eg, papules, vesicles). These findings are characteristic of chickenpox, or primary infection by varicella-zoster virus (VZV).
VZV infection is most common in fully unvaccinated patients because vaccination is protective from disease in immunocompetent patients. However, vaccination is a 2-dose series administered at age 1 and 4; breakthrough infections can occur in partially vaccinated patients, as in this 3-year-old patient who has likely received only 1 dose of the varicella vaccine based on age and may have been exposed to the virus over the course of international travel (eg, recent trip to South Africa).
Approximately 2 weeks after exposure to airborne particles, patients with chickenpox develop a brief prodrome (eg, fever, malaise) followed by onset of rash within 24 hours. The rash is initially maculopapular but rapidly becomes intensely pruritic and vesicular, involving the trunk, face, and extremities. The vesicles can become pustular and subsequently crust over. Successive crops of vesicles appear daily over a week, resulting in lesions at different stages of progression. Breakthrough infection in partially vaccinated patients is often milder (eg, lower fever, fewer lesions) than in fully unvaccinated patients.
(Choice A) Eczema herpeticum is caused by herpes simplex virus and manifests as fever with a painful vesicular rash overlying areas of skin affected by atopic dermatitis. This patient's lesions are itchy (not painful), and he has no history of atopic dermatitis.
(Choice B) Hand-foot-and-mouth disease is caused by coxsackievirus and presents with a rash that may be vesicular, but, in contrast to this patient's diffuse rash, the lesions predominantly involve the hands and feet. Moreover, oral ulcers are typical and are not seen here.
(Choice C) Roseola, caused by human herpesvirus 6, causes high fever followed by a diffuse, maculopapular (not vesicular) rash that appears as the fever abates.
(Choice D) Rubella infection is characterized by a maculopapular rash that begins on the face and spreads cephalocaudally. Vesicular lesions do not occur.
(Choice E) Scabies causes a papular/vesicular rash that is intensely pruritic. However, in contrast to this patient's diffuse rash, the classic distribution of scabies involves the interdigital webs, palms/soles, flexor surfaces of the wrists, and periumbilical area. Moreover, systemic symptoms (eg, fever) are not expected in scabies.
Educational objective:
Chickenpox is characterized by successive crops of intensely pruritic macules/papules, vesicles, and pustules. Breakthrough infection, which is typically a milder infection with lower fever and fewer lesions, can occur in partially vaccinated patients.