Histopathological Findings in Nail Clippings With Periodic Acid-Schiff-Positive Fungi.

Background: Periodic acid-Schiff (PAS) staining of nail clippings is an adjunct diagnostic tool for onychomycosis.

Objective: To detect histopathological findings as clues to the presence of PAS-positive (+) fungal elements in nail clippings.

Methods: Four hundred sixteen consecutive nail clippings suspected of onychomycosis were stained with hematoxylin and eosin, and with PAS stains. All cases were studied histopathologically. The clinical files of the cases with neutrophils were reviewed.

Results: PAS+ staining for fungi were demonstrated in 159 (38%) of the nail clippings. Neutrophils, parakeratosis, plasma globules, and bacteria were observed in 43 (27%), 108 (67%), 80 (50%), and 80 (50%) of the PAS+ cases, respectively, and in 17 (6%), 109 (41%), 84 (32%) and 140 (54%) of the PAS- cases, respectively (P < 0.01). Neutrophils showed by far the highest specificity (93%), although with low sensitivity (27%) for the presence of PAS+ fungi. Among the 43 PAS+ and 17 PAS- specimens with neutrophils, only 1 (2.3%) and 3 (17%) had overt psoriasis, respectively.

Conclusion: Neutrophils in nail clippings may serve as a clue for onychomycosis. PAS staining with neutrophils is not necessarily associated with psoriasis.