A 3-year-old boy is brought to the office by his father due to a rash near his buttocks for 2 weeks. The father states, "He has been scratching his bottom during the day. We have tried several over-the-counter barrier ointments and antifungal creams to soothe the area, but nothing seems to help." The patient is toilet-trained during the day but uses diapers at night. He usually stools twice a day without straining, but for the last few days he has had pain with bowel movements and blood on the toilet paper after wiping. He has had no recent illnesses and has been eating and sleeping well. The patient has no chronic medical conditions, and vaccinations are up to date. His 8-year-old sister had pharyngitis a few weeks ago but is now recovered after taking antibiotics. Temperature is 37.2 C (99 F). Physical examination shows a well-appearing child with a bright red, sharply defined rash that extends 2 cm circumferentially around the anus. There are 2 fissures in the perianal region. No other rashes are present on the body. Which of the following is the most likely diagnosis in this patient?

Question

A 3-year-old boy is brought to the office by his father due to a rash near his buttocks for 2 weeks.  The father states, "He has been scratching his bottom during the day.  We have tried several over-the-counter barrier ointments and antifungal creams to soothe the area, but nothing seems to help."  The patient is toilet-trained during the day but uses diapers at night.  He usually stools twice a day without straining, but for the last few days he has had pain with bowel movements and blood on the toilet paper after wiping.  He has had no recent illnesses and has been eating and sleeping well.  The patient has no chronic medical conditions, and vaccinations are up to date.  His 8-year-old sister had pharyngitis a few weeks ago but is now recovered after taking antibiotics.  Temperature is 37.2 C (99 F).  Physical examination shows a well-appearing child with a bright red, sharply defined rash that extends 2 cm circumferentially around the anus.  There are 2 fissures in the perianal region.  No other rashes are present on the body.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d643_152b_bc81_cde93778e107_MD0003_00 This patient most likely has perianal streptococcal dermatitis, a superficial infection with Streptococcus pyogenes (group A Streptococcus). perianal streptococcal dermatitis This condition presents in infants and young children with bright, sharply demarcated, confluent erythema in the perianal or perineal region. Associated features include perianal pruritus and pain, particularly with stooling. In some patients, perirectal fissures and blood-streaked stools may occur. Due to pain while stooling, patients may also have constipation from withholding. Although patients often do not have concomitant streptococcal pharyngitis, a close contact may have had a recent streptococcal infection (eg, cellulitis, pharyngitis). The diagnosis can be suspected based on clinical features alone and confirmed with a perianal bacterial culture. Treatment is with oral beta-lactam antibiotics (eg, penicillin, amoxicillin). (Choice A) Candidal diaper dermatitis presents with bright red erythema, but its distribution is usually more widespread throughout the diaper area and includes satellite lesions and skinfold involvement. In addition, the lack of response to antifungal creams makes Candida infection less likely. Candidal diaper dermatitis satellite lesions (Choice B) Irritant diaper dermatitis presents with erythema and skin breakdown in the diaper area due to prolonged exposure to urine or stool, particularly in the setting of diarrhea. This patient's lack of response to barrier ointments and use of diapers only at night make irritant diaper dermatitis less likely. Irritant diaper dermatitis (Choice D) Pinworm infection is caused by Enterobius vermicularis and presents with perianal pruritus, classically at night rather than during the day. Rectal bleeding can occur due to excoriations, and mild perianal erythema may be seen. However, the rash is not painful and not associated with perirectal fissures. (Choice E) Pediatric seborrheic dermatitis most commonly presents in infancy with cradle cap or moist-appearing erythema along the skinfolds (eg, neck, axillae, thighs). Patients are typically asymptomatic. This patient's age, pruritus, and pain make seborrheic dermatitis unlikely. Educational objective: Perianal streptococcal dermatitis presents in young children as a bright red, sharply demarcated, perianal rash associated with pruritus and pain. Treatment is with beta-lactam antibiotics. References: Perineal infectious dermatitis: an underdiagnosed, unremitting and stubborn condition. (http://www.ncbi.nlm.nih.gov/pubmed/30627524)

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