Background: Nail clipping microscopy is a valuable diagnostic tool in onychomycosis but has not been explored for the diagnosis of onychodystrophy caused by psoriasis. The objective of this study was to try to establish criteria for the diagnosis of psoriasis by this method.
Methods: Cross-sectional study of adult patients with clear-cut psoriasis is divided into 2 groups: (1) with onychodystrophy and (2) with clinically normal nails. The patients were evaluated regarding gender and age, among other clinical variables. The samples were coded to allow blinded microscopic interpretation for nail plate and subungual region thickness and for the presence or absence of corneocytes, neutrophils, serous lakes, blood, bacteria, onychokaryosis, hypereosinophilic nuclear shadows, and fungi.
Results: Ninety-six patients with psoriasis were enrolled in this study. There were 40 male and 56 female subjects; ages varied from 16 to 87 years (mean, 51 years). Onychodystrophy was detected in 51 patients (53%). On average, nail plate thickness and subungual region thickness measured 0.44 and 0.19 mm in the onychodystrophy group and 0.41 and 0.14 mm in the clinically normal group (P > 0.05). Dystrophic nails presented 4.5 layers of corneocytes, on average, in contrast to the average of 2.4 in the clinically normal-looking nails (P = 0.0004). Neutrophils (12%), serous lakes (46%), blood collections (11%), bacteria (74%), fungi (20%), onychokaryosis, and hypereosinophilic nuclear shadows were all more common in the onychodystrophy group but not in a statistically significant standard when compared with the other group (P > 0.05).
Conclusions: Nail clippings from patients with psoriasis present abnormally thickened subungual region with prominent hypercorneocytosis, serous lakes, bacteria, neutrophils, and blood collections. If fungi are present, usually there are spores. Clinically, normal-looking nails in patients with psoriasis can present microscopic abnormalities.