Scabies, crusted: A severe form of scabies caused by delayed treatment of the initial infestation, characterized by mite-filled lesions covered with scabs. These lesions often fall victim to secondary infections, as with Staphylococcus bacteria. Crusted scabies is most common in people with immune-system problems, including AIDS, diabetes, and lupus. Also known as keratotic scabies, Norwegian scabies.