January 2006

Fig4

Fig5

Diagnosis: Crusted (Norwegian) Scabies

Scabies Prep and Pathology: Scabies prep reveals a mite as well as an egg (Fig4). H&E reveals multiple mites within the stratum corneum (Fig5).

Discussion: This patient was treated with oral Ivermectin as well as permetherin 5% to his entire body. The topical steroids were discontinued.

Scabies is caused by infestation with the mite, Sarcoptes scabei var humanus. The hallmark of classic scabies is intractable pruritus, especially severe at night. Classic scabies typically involves the web spaces, sides of the fingers, flexor surfaces of wrists and elbows and anterior axillary folds. Other common sites include the penis and scrotum in men and areolae in women.
Norwegian scabies, a special form of scabies, has a predilection for individuals who are immunocompromised, aged, physically debilitated, or mentally impaired. Extensive widespread crusted lesions appear with thick hyperkeratotic scales over the elbows, knees, palms, and soles. Clinically, symptoms may mimic psoriasis or Darier's disease. Finger or toenail involvement may simulate psoriasis or onychmycosis. The severe itch that is usually reported with typical scabies may be reduced or absent in Norwegian scabies. These individuals can be infested with thousands to millions of mites at a time. If there is no known predisposing condition, patients with crusted scabies should be tested for AIDS. Patients with crusted scabies may develop bacteremia as a consequence of infection of fissured and excoriated skin.

Diagnosis may be made by direct examination with a scabies prep of scales or burrows revealing mites, eggs or scyballa (feces).

Treatment for scabies includes topical scabicides including permethrin 5% cream (a synthetic pyrethroid), lindane 1% or precipitated sulfur (6%) in petrolatum. Ivermectin is a systemic antiparasitic FDA approved for onchoceriasis and strongyloidiasis. It is an effective treatment for scabies in doses of 200 micrograms/kg. Treatment for crusted scabies often requires repeated applications and the sequential use of two or more agents may be necessary. It is important to treat the entire skin, including the scalp and face as well as directly applying under nails. Due the huge numbers of mites, isolation until treatment is complete is important. The environment and fomites need to be treated as well. Prophylactic therapy of exposed individuals is also indicated

References:

Fitzpatrick's Dermatology in General Medicine, 5th ed. (Freedberg IM, Eisen AZ, Wolff K, Austen KF, Goldsmith LA, Katz SI eds.). New York: McGraw-Hill, 1999.
Huffam SE, Currie BJ. Ivermectin for Sarcoptes scabiei hyperinfestation. Int J Infect Dis. 1998 Jan-Mar;2(3):152-4.
Cestari SC, Petri V, Rotta O, Alchorne MM., Oral treatment of crusted scabies with ivermectin: report of two cases. Pediatr Dermatol. 2000 Sep-Oct;17(5):410-4
Scheinfeld, N.et al. Controlling scabies in institutional settings: a review of medications, treatment models, and implementation. Am J Clin Dermatol. 2004;5(1):31-7.
Takeshita T. et al, Crusted (Norwegian) scabies in a patient with smoldering adult T-cell leukemia. J Dermatol. 2000 Oct;27(10):677-9.

This case is presented by Gina Bowers MD and Julie Lowe MD