Author: Dr Stanley Leong, Dermatology and Paediatric Registrar (2023)
Reviewing dermatologist: Dr Ian Coulson (2023)
Edited by the DermNet content department
A 34-year-old woman with trisomy 21 presented with a rapidly worsening rash of 4 months. The rash was associated with marked scratching that started on her hands then spread throughout the body. She had no preceding skin disorders.
Other family members had a recent history of itch that improved with time but hers deteriorated.
On examination, she appeared miserable with thick, crusty plaques over her forehead, nails, fingers, wrists, toes, and soles with multiple linear fissures.
Dermoscopic examination showed many live mites and burrows.
Crusted scabies is a highly contagious hyperinfestation with Sarcoptes scabiei var hominis a parasitic mites, presenting in immunocompromised patients. It is previously known as Norwegian scabies.
It is estimated that individuals with crusted scabies have up to 4,000 mites/g of skin. Patients are often infested with over 1 million mites. The majority of patients with normal scabies are infested with only with around 10–20 mites.
Scabies is readily diagnosed clinically and confirmed by identification of mites or eggs on dermoscopic or microscopic examination of burrows or scale in crusted disease.
Treatment requires oral ivermectin and topical insecticides:
Family members, carers, and close contacts should also be screened for scabies and treated accordingly. Regardless of examination findings, all family members who have had close contact with the index case should be treated with a topical scabicide and should repeat treatment in one week.
Risk factors for crusted scabies include:
