Rosh Pediatrics Practice Exam

The detection of an organism confirmed by a potassium hydroxide (KOH) preparation in a 10-year-old boy with an intensely pruritic rash suggests a diagnosis of scabies caused by Sarcoptes scabiei. This parasite is a common cause of intense itching and rashes in children and is typically associated with close contact situations, which can lead to outbreaks in schools or families. KOH preparations are commonly used to prepare skin scrapings that can help visualize certain types of infections, particularly those caused by fungi or scabies mites. When skin scrapings from a suspected scabies lesion are examined under a microscope after KOH treatment, the scabies mites, eggs, and fecal matter can be identified, confirming the diagnosis. Demodex folliculorum is a mite that colonizes human hair follicles but is typically associated with acne-like lesions and is not confirmed through KOH preparation. Pediculus humanus refers to lice, which would present with a different type of rash and is diagnosed through visual examination rather than KOH preparations. Pyemotes tritici, also known as harvest mite, can cause pruritic rashes but is not typically confirmed using KOH preparation either. The intense pruritus, along with the findings