DISCUSSION
After a lengthy search, a single scabies adult (scabies sarcoptei var humanus) was found embedded in the scales. Scabies is one of the two most common ectoparasitic infestations in this country (the other being head lice).
Paradoxically, it is one of the most over- and under-diagnosed medical conditions worldwide. It is transmitted from person to person and can only be acquired from close, prolonged contact with another human who has the condition. This case illustrates some of the difficulties involved in making the diagnosis.
While it is vital to consider scabies in the differential for constant, severe itching, there are situations in which it can be ruled out. People who live alone and/or avoid physical contact with other people cannot get scabies. It can only be acquired from an infected person—not from a dog, cat, or inanimate object. In this case, the patient lived alone, but she hosted sleepovers with her grandchild—the likely source of this infestation.
Scabies can manifest as an eczematoid rash that will not respond to topical or systemic steroids. Conversely, when eczema patients are misdiagnosed with scabies, permethrin cream worsens the condition. Therefore, once scabies is considered in the differential, a KOH prep is indicated for a definitive diagnosis.
In terms of treatment, it does little good to simply treat the patient in question. The entire family (and/or close contacts) needs to be treated simultaneously—but before that, the source of the scabies needs to be identified. Failure to address all of these factors often leads to “treatment failure.”
The case patient was successfully treated with a combination of permethrin cream and oral ivermectin, according to the standard regimen (two treatments, seven to 10 days apart).
TAKE-HOME LEARNING POINTS
- Scabies can only be acquired from close, prolonged contact with another human who has the condition.
- Intractable itching and failure to respond to treatment (ie, topical and systemic steroids) are its dependable diagnostic features.
- Scraping suspected scabetic lesions (tiny vesicles, dried papules, or—if you’re lucky—a burrow) and examining them under 10x microscopy is preferable for confirmation of the diagnosis.
- The whole family must be treated in synchrony with the patient.
- It is essential to identify the source of the scabies (eg, spouse, boyfriend/girlfriend, child) to successfully eradicate the problem.