To the Editor: The medical mystery in the April 5 issue1 involveda 34-year-old bank employee who presented with black discolorationsof the skin (Figure 1A) on all her fingers. The discolorationshad developed in the evening after work. A skin-biopsy specimenof the black spots revealed brownish deposits of elemental silverin the corneal layer (Figure 1B), with a fluorescent aspecton the dark-field microscopical examination (Figure 1C), whichis typical of elemental silver. Infrared spectroscopy and microanalysiswith x-rays showed that some of the bills the patient had beencounting (Figure 1D) were prepared with a combination of silvernitrate and petroleum jelly, a method often used to find a thief.Silver nitrate diffuses into the epidermis and reacts with chloridefrom sweat to form silver chloride, which is photochemicallyreduced by ultraviolet light to form colloidal particles ofmetallic silver; these appear black and persist in the epidermis.An advantage of this method of trapping thieves is that usuallyother persons or objects cannot be contaminated, because thereaction of silver nitrate and chloride produces silver chlorideso rapidly. The discolorations cannot be removed by washing,but they disappear after 1 to 2 weeks with normal epidermalturnover. The thief in this case was never identified.
Figure 1. Elemental Silver in the Corneal Layer of the Epidermis.
A skin-biopsy specimen of the black spots on the finger (Panel A) revealed brownish deposits of elemental silver in the corneal layer (Panel B), with a fluorescent aspect on the dark-field microscopical examination (Panel C). Infrared spectroscopy and microanalysis with x-rays showed that some of the bills the patient had been counting (Panel D) had been prepared with a combination of silver nitrate and petroleum jelly.
Stefan Schanz, M.D. Gisela Metzler, M.D. University of Tübingen D-72076 Tübingen, Germany stefan.schanz{at}med.uni-tuebingen.de
Editor's note: We received 960 responses to this medical mystery,from 75 countries. Of these, 57% were from physicians in practice,16% from physicians in training, 15% from medical students,and 12% from other readers. This medical mystery sparked quitea bit of interest among scientists associated with law enforcement.
Overall, 76% of the respondents identified an environmentalexposure to an exogenous substance as the cause of the blackspots; most of these respondents suggested ink of some kindfrom either the bills or an associated copy machine, but a subgroup(24%) correctly identified silver nitrate as the offending substance.The remaining 24% of the respondents suggested numerous diagnoses,including endocarditis, anthrax, trauma, vasculitis, and melanoma.Remarkably, 4% of the respondents correctly identified the motivefor the activity — detection of thievery.
References
Schanz S, Metzler G. A medical mystery -- skin discolorations in a bank employee. N Engl J Med 2007;356:1455-1455. [Free Full Text]
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