Challenges in Public Health: The Diagnosis and Treatment of Crusted Scabies

Introduction: Common scabies is a parasitic dermatologic condition that often presents as an extremely pruritic rash. A rare and highly contagious variant of common scabies is crusted scabies, formerly known as Norwegian scabies. While infection with common scabies typically involves 10 to 20 mites, individuals with crusted scabies are burdened with thousands to millions of mites. Crusted scabies is characterized clinically by hyperkeratotic papules and plaques, most commonly on the palms and soles. Due to the variety of presentations seen in scabies, it can be difficult to diagnose. Case Presentations: We present four cases of crusted scabies. An 89-year-old male with a history of dementia presented with a two-month history of a generalized pruritic rash. A 22-year-old male with a history of trisomy 21 presented with a 10-month history of mildly pruritic rash on the hands. A 54-year-old female with a history of trisomy 21 and cutaneous T-cell lymphoma presented with a three-week history of a generalized pruritic rash. Lastly, a five-year-old male with acute lymphoblastic leukemia with a minimally pruritic rash on his hands and elbows that had spread to the genitals. The patients were diagnosed with skin scrapings or biopsy showing scabies mites. These patients were all treated with extended courses of oral and topical anti-parasitic medications. Discussion/Conclusion: Crusted scabies poses a significant challenge to public health as a severe variant of scabies associated with high morbidity and mortality. It is most commonly seen in persons who are immunosuppressed, have an underlying neurologic disorder, or are immobile. Patients may present with skin eruption and pruritus. Patients can also present with severe illness such as erythroderma, which poses a risk for hypothermia, acute respiratory distress syndrome, sepsis, and high-output heart failure. Scabies-related mortality in crusted scabies is high. Management of crusted scabies is different than for other types of scabies because the patient is infested with large numbers of mites. Patients may also have an altered immune response. Treatment of crusted scabies requires a combination of oral and topical treatments. Lastly, the large number of mites in crusted scabies requires more rigorous evaluation and treatment of contacts than other types of scabies. This is necessary to prevent or limit scabies outbreaks and re-infection. As many patients with crusted scabies live in congregate facilities, this requires prompt evaluation of contacts with treatment of cases and public health treatment of asymptomatic residents, staff, and visitors.