Histologic Examinations of Fungous Infections of the Nails

Abstract

In the study of fungous infections of the nail the histologic examination has been almost entirely neglected by dermatologists. While other nail conditions frequently are examined histologically, investigation of cases of onychomycosis has been confined largely to the microscopic examination of the nail substance, softened in potassium hydroxide. The recognition of fungi in potassium hydroxide preparations is relatively easy and, for this reason, it appears to be unnecessary to look at the histologic picture of the fungous infected nail. Direct microscopic examinations of the nail material in potassium hydroxide, however, yield no certain proof that the fungus exists in the nail plate. It may be that the fungus is lying on the nail plate or below it, without infecting the nail. Proof of invasion of the fungous infection into the nail-plate itself is found only by means of the histologic examination. Furthermore, such examination seems even more important when one considers that frequently the results of cultures of fungi from scrapings of the nail are negative in spite of the fact that the examination in potassium hydroxide preparations shows that fungi are present. It may be that cultures from nail substances yield positive results less often than do cultures from the skin because of technical difficulties or contaminating overgrowth of non-pathogenic fungi or bacteria.