DISCUSSION
Microscopic evaluation revealed a scabies adult, still moving among the dead cells. The paucity of organisms was probably a result of the prior treatment with permethrin, which confused the issue. When scabies is suspected, there’s only one way to confirm it: Perform a KOH prep. Otherwise, it’s just guesswork.
This particular patient was under the (faulty) impression that because her permethrin treatment failed, she didn’t have scabies. But a single treatment with topical antiscabetic cream is rarely curative. It must be done twice, seven to 10 days apart, to kill organisms newly hatched from eggs lain in the skin. In many cases, oral ivermectin is needed as well.
The itching experienced with scabies is due to an allergic response to scabetic material (droppings, tissue juice). The resultant eczematous rash can be very challenging to deal with.
Three other people live in the patient’s house, and it’s likely that these family members have been infested over several months’ time. They need treatment as well and will require two applications of cream.
Thought should also be given to how the patient acquired the infestation, lest she get it again. This may result in the need to avoid contact with certain people or confront them about their possible role as the source.
TAKE-HOME LEARNING POINTS
• The itching and rash of scabies result from an allergic reaction to the scabetic elements deposited in the skin. This reaction can closely resemble eczema.
• A single treatment of permethrin cream is unlikely to clear scabies. In order to have an effect on the eggs lain in the skin (which hatch in seven to 10 days), two treatments are necessary.
• Many cases of scabies will survive permethrin treatment, so consider adding ivermectin (oral antiscabetic medication) to the regimen.
• All family members living in the same house must be treated at the same time, lest they re-infest one another.
• KOH prep is the gold standard for diagnosing scabies.