KOHALA COAST, HAWAII — Attack hyperkeratotic scabies both topically and systemically or your treatment will fail, Timothy G. Berger, M.D., said at a conference sponsored by the Center for Bio-Medical Communications Inc.
He divides patients with scabies into two categories to guide management—those with a low burden or a high burden of disease. For the typical patient with a low burden, two applications of permethrin 5% cream a week apart will cure 95% of cases.
But a double whammy usually is needed for patients with a high burden of disease—those with crusted or hyperkeratotic scabies, AIDS and scabies, or scabies acquired while in a long-term care facility or prison, said Dr. Berger of the University of California, San Francisco.
He prefers to use these two categories because patients with a high burden of disease may present with multiple papules instead of crusts, but need the combination therapy used for crusted scabies.
The combination treatment consists of weekly applications of permethrin 5% cream for 3–6 weeks plus ivermectin 200 mcg/kg every 2 weeks for two (or occasionally three) doses. The patient should show improvement by 3 weeks and continue to gradually improve.
Don't try to save a buck by skimping on the ivermectin, Dr. Berger warned. Don't round down the dose but, rather, give the full dose of ivermectin (usually 12–18 mg), and allow plenty of time to treat. In appropriate doses, the combination therapy has never failed him.
In a typical case, a family brought in an 87-year-old woman who had had 6 months of severe itching, though no one else in the family was itching.
The patient had failed treatment with multiple courses of permethrin, systemic steroids, and other medications.
She had a widespread papular eruption on her trunk, proximal extremities, and face, showing focal plaques, some of which were markedly hyperkeratotic, Dr. Berger said.
“The British describe this as looking like a fine white sand on the skin. That's exactly what it looks like,” Dr. Berger said.
Her history was a tip-off: After a hip replacement 9 months earlier, she had spent time in a long-term care facility for rehabilitation. Scrapings of lesions on the soles of her feet were loaded with scabies mites and feces.
Don't be dissuaded from suspecting scabies just because a patient has failed permethrin treatment or family members seem unaffected, Dr. Berger advised.
Treat the whole family, but not necessarily immediately. Family members who are affected get immediate treatment, but otherwise Dr. Berger waits to treat the family until the primary patient has been treated, so that the patient is no longer infectious.
High-burden cases often involve the scalp, so instruct patients to apply permethrin to the scalp too, he advised. Ivermectin won't help scabies involving the nail plate, so consider more aggressive treatments for nail scabies.
Ivermectin is secreted in sebum, he noted, which is one reason monotherapy may not work in the elderly, children, malnourished patients, or people with Down syndrome, all of whom make less sebum.
Immunosuppression plus neural disease puts patients at risk for crusted scabies, one reason that people with AIDS or Down syndrome are at higher risk for crusted scabies, he said.