Case #159 – July, 2005

A 25-year-old woman had a few mildly scaly lesions on her forehead. She saw her physician and initially it was thought that she had a fungal lesion. Figure A-C show what was seen in skin scrapings from the lesion. The object shown was approximately .25mm long. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

The images showed a follicle mite (Demodex sp.). There are two species of Demodex that are associated with humans, D. folliculorum, which lives in the hair follicles and D. brevis, which lives in the sebaceous glands, although there are many species that infest wild and domestic animals. The two species are similar in appearance. Diagnostic features included:

the size, which was in range for Demodex spp. (0.1 mm to 0.4 mm).
an elongated body that was somewhat cigar-shaped (the body of D. brevis may be somewhat shorter).
eight very short, segmented legs.

In general, these mites are harmless, although in some instances they may cause irritations. More images of Demodex can be seen here, on the scabies pages. Please note, Demodex is shown with scabies as a differential diagnosis, especially when examining tissue sections. Demodex spp. are not causative agents of scabies in humans.