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| Figure 1 | Figure 2 |
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A 24-year-old man presented with a widespread, nonpruritic eruption that had begun 4 months before admission. He had no benefit from topical keratolytics applied to his hands and forearms. Dermatological examination revealed erythema and scaling over the whole body sparing some areas of his face and scalp (Figs. 1, 2). His nails were normal. He reported that some family members had pruritus, without crusting. He was healthy and had no history of other unusual infections suggestive of immunocompromise and was taking no immunosuppressive medications.
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| Figure 3: numerous mites present within the hyperkeratotic epidermis (H&EX100) |
KOH skin scrapings and histopathological examination of skin biopsy revealed numerous mites, eggs and feces (Fig. 3). Laboratory tests including complete blood count, serum chemistry panel, quantitative immunoglobulins were all within normal limits. Serum antibody to human immunodeficiency virus was negative.
He was treated with topical permethrin (5% cream for 12 hours once per week for 6 weeks), precipitated sulfur (6% in vaseline, 6 days per week for 3 weeks). The crusted skin lesions improved and disappeared completely within 3 weeks. We administered permethrin cream to the family members sharing the house. He remained free of scabies over the following 1 year.
Crusted or Norwegian scabies is a rare massive clinical variant of infestation with Sarcoptes scabiei var. hominis [1, 2, 3]. In common scabies, the number of parasites infesting the epidermis is limited, probably because the host is immunocompetent and the defensive act of scratching may eliminate some of the parasites and acarian tunnels [4, 5]. In crusted scabies (CS) there is unlimited parasite multiplication due to the defective immunologic response of the host or because there is physical limitation or lack of awareness of pruritus. These situations would include neuropsychiatric disorders, osteoarticular deformities, muscular atrophy, or other neuromuscular problems associated with loss of or diminished sensation [2, 3, 4]. In CS, numerous parasites colonize in the epidermis, inducing characteristic hyperkeratotic changes [5].
Clinically CS is characterized by extensive hyperkeratosis and crusting of the skin, notably on acral areas [5]. The eruption is generally severe on the limbs, but may extend to the face and scalp [4]. Erythema and scaling are of varying degrees and may evolve into erythroderma [4, 5]. Pruritus is usually absent but can be moderate to severe [2, 5]. Nail abnormalities may be seen [4]. Diagnostic confusion of CS with primary skin conditions such as psoriasis, seborrheic dermatitis, contact dermatitis, and keratosis follicularis is common [5]. The peculiar sandlike quality of the scale may suggest the diagnosis. Additionally, the occurrence of typical scabies in contacts is frequently the clue to the diagnosis [6].
Our patient is exceptional in that he did not have any of the risk factors commonly associated with a propensity to develop CS. In the literature only three healthy patients, one pregnant [7], one infant [8], and one child [2] have been reported. Erythroderma in adults is caused by drug reactions, psoriasis, hematologic malignancies (cutaneous lymphoma), seborrheic dermatitis, atopic dermatitis, pityriasis rubra pilaris, lichen planus, pemphigus foliaceus, and crusted scabies [9]. In erythroderma rates of CS from two different centers have been reported as 1 percent and 1.25 percent, respectively [10, 11]. CS should be kept in mind in the differential diagnosis of an erythrodermic patient.
Treatment includes oral ivermectin as well as topical scabicides. Keratolytic agents may be added to conventional human scabies treatments to permit improved penetration of scabicides through the hyperkeratotic crusts [2, 3, 4]. Relapses may occur from subungual spaces and the scalp, which are difficult areas to reach with topical products [4]. Recently, several studies have shown that ivermectin is effective and safe for the treatment of crusted scabies [2, 4, 5, 12, 13, 14]. In our patient, we achieved an excellent response with topical treatments.
© 2006 Dermatology Online Journal