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Crusted lesions on palms

An 86-year-old woman with a high-grade fever was brought to the emergency department for evaluation. She lived in a nursing home and was in a persistent vegetative state. She had multiple erythematous keratotic papules and plaques on her face, trunk, and limbs, as well as thick, scaly brownish plaques on both of her hands. Skin scrapings from her palms were sent to the lab.

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Based on the physical findings and results of the lab work, the patient was given a diagnosis of crusted scabies.

Crusted scabies, also known as Norwegian scabies, is an uncommon form of scabies infestation. The causative organism is the burrowing mite Sarcoptes scabiei (the same organism involved in ordinary scabies). The difference, though, is that the level of infestation with crusted scabies is more severe.

Definitive diagnosis depends on microscopic identification of the mites, their eggs, eggshell fragments, or mite pellets. Patients also have extremely elevated total serum immunoglobulin E and G levels, and are predisposed to secondary infections.

Patients with dementia or mental retardation and those who are immunocompromised are most susceptible to the disease. (The patient described here had a history of dementia.) In nursing homes, patients with unrecognized crusted scabies are often the source of transmission to other residents and staff members. A crusted scabies host may harbor more than one million mites.

Because of the large number of mites in the hyperkeratotic lesions, this disease is difficult to manage. Daily application of topical scabicidal agents such as 5% permethrin cream, 1% lindane cream, 6% to 10% sulfur-based topical agents, or 12.5% benzyl benzoate lotion is recommended. A mixture of keratolytic agents on the hyperkeratotic areas might help the topical medication gain access to the target areas. Another effective approach is prescribing a single oral dose of ivermectin 200 mcg/kg with a topical preparation. Most modern treatments of crusted scabies involve the use of oral ivermectin and topical permethrin given at the time of diagnosis and repeated in 7 to 10 days. Clothes, bedding, and towels should also be decontaminated by machine washing them in hot water and drying them in the hot cycle.

In this case, the patient was admitted to the intensive care unit and her skin lesions were treated with topical mesulphen once daily for 10 days. Gradually, the lesions improved and she returned to the nursing home a month later.

Adapted from: Liaw FY, Huang CF, Fang WH, et al. Asymptomatic crusted lesions on the palms. J Fam Pract. 2012;61:43-46.

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