Case #416 – March 2016

An 81-year-old female developed hyperkeratotic plaques between her fingers and toes while undergoing aggressive chemotherapy for acute myeloid leukemia (AML). Skin scrapings were performed on the plaques and sent to Microbiology for routine work-up. Figures A and B were observed by the attending microbiologist on a direct prep made from the skin scrapings. The object in Figure A measured approximately 400 micrometers in length. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of crusted scabies caused by the human itch mite, Sarcoptes scabiei. Diagnostic features included:

adult mites (Figures A and B) within the size range for S. scabiei, possessing a sub-spherical shape, reduced legs, and prognathous mouthparts.
mite fecal pellets (also known as scybala, Figure B).

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This case and images were kindly provided by the Mayo Clinic, Rochester, MN.

DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.