Eleven Years of Itching: A Case Report of Crusted Scabies
Crusted scabies is a rare and highly contagious form of scabies that is characterized by uncontrolled proliferation of mites in the skin, extensive hyperkeratotic scaling, crusted lesions, and variable pruritus. We report the case of a 48-year-old man with an 11-year history of pruritic, hyperkeratotic, psoriasiform plaques and widespread erythematous papules that was diagnosed as crusted scabies.
Practice Points
- Crusted scabies can mimic a variety of conditions such as psoriasis, eczema, seborrheic dermatitis, and contact dermatitis. Therefore, suspicion is the prerequisite for disease control.
- Scabies usually is found in individuals with a compromised immune system as well as those with decreased sensory functions. Thus patients should be investigated for an underlying immunodeficiency.
- Treatment can be challenging, and effective management of the condition requires a keratolytic agent in conjunction with a scabicidal agent.
Unlike classic scabies, crusted scabies usually does not present acutely, and it usually is insidious at onset. The eruption typically has 2 components: localized horny plaques and a more distinct erythema.3 Crusted scabies can mimic a variety of conditions such as psoriasis, eczema, seborrheic dermatitis, Darier disease, contact dermatitis, and pityriasis rubra pilaris.7 When pruritus is resistant to permethrin therapy, as in our patient, crusted scabies often is misdiagnosed as eczema or contact dermatitis. Topical and systemic corticosteroids often are prescribed, causing progression to scabies incognito.
The diagnosis of crusted scabies is confirmed by examination of scrapings and biopsies, as in classic scabies; however, treatment can be challenging due to compromised immunity, a large mite burden, and limited penetration of topical medications into the hyperkeratotic lesions. Thus treatment should include both keratolytic and scabicidal agents to remove the crusts, reduce the mite load, and enhance the scabicidal therapy.1 Our patient and his affected family members had previously been treated with topical permethrin several times without any benefit. Oral ivermectin has been proven to be effective but is not available in Turkey. Therefore, we treated the patient and his household contacts (other extended family members treated separately) with modified Wilkinson ointment (goudron végétal 12.5%; sulfur 12.5% in petrolatum) for 3 consecutive days, which is known to have both a keratolytic and scabicidal effect.8-11
Conclusion
This case highlights the importance of obtaining a complete family history, skin examination, and thorough investigation for underlying immunodeficiencies that can lead to a predisposition for crusted scabies. It is important to note that the treatment of crusted scabies can be challenging, and effective management of the condition requires a keratolytic agent in conjunction with a scabicidal agent.
