Subungual hyperkeratosis as a diagnostic cue in crusted scabies.

Crusted scabies is a severe and uncommon variant of Sarcoptes scabiei var. hominis infestation and typically arises in older adults with impaired cellular immunity. Secondary erythroderma and bacteremia are feared complications that may lead to increased morbidity. Herein, we report a case of crusted scabies with subungual involvement in a 65-year-old man with vascular dementia, schizophrenia, and chronic obstructive pulmonary disease presenting from an assisted living facility. At presentation, the patient was erythrodermic, alongside diffuse scaling with scattered excoriations and marked palmar/subungual hyperkeratosis. Laboratory investigations revealed methicillin-resistant Staphylococcus aureus bacteremia, coronavirus disease 2019 infection (COVID-19) and markedly elevated serum immunoglobulin E levels. The patient was started on vancomycin, topical permethrin 5%, and oral ivermectin, with subsequent resolution of the rash and pruritus prior to discharge from the hospital. This case highlights subungual hyperkeratosis as a practical diagnostic clue and potential mite reservoir in crusted scabies presenting as erythroderma. Recognition of this morphology can prompt immediate bedside microscopy, combined topical and systemic scabicidal therapy, and contact precautions to reduce nosocomial transmission.