Case #314 – December, 2011

A 25-year-old man sought medical attention for a nodule on his right hand that had developed about a year after returning from travel to Liberia. The nodule was surgically excised and a tangled mass of thin, white worms was observed within. The worms were preserved in 10% formalin and sent to CDC-DPDx for identification. Figure A shows the mass of worms; Figures B and C show what was observed at 100x after partial clearing in lactophenol. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

This was a case of onchocerciasis caused by Onchocerca volvulus. Morphologic features shown in the images included:

whitish, thread-like worms that were recovered from a skin nodule (Figure A).
transverse (annular) thickenings at regular intervals (Figures B and C) along the worms’ cuticle.