Detection rate of pustules in palmoplantar pustulosis with dermoscopy

In this study, dermoscopy was applied to determine the site of skin biopsy in cases of palmoplantar pustulosis (PPP) with invisible tiny pustules or vesicles. Fifty-two clinically diagnosed PPP patients (11 men and 41 women) were observed by a dermoscope and underwent skin biopsy. Nineteen patients had visible pustules, whereas 33 had no visible pustules. Pustules were detected by a dermoscope on palmoplantar lesions in 17 of the 33 PPP patients. In contrast, 16 patients showed no presence of pustules or vesicles observed by a dermoscope. In this group, biopsy specimens were taken from scaly lesions. Out of the 16 patients, 10 histologically showed pustules in the epidermis. We finally detected pustules for 46 patients among 52 who were clinically diagnosed with PPP. As a result, we detected pustules in PPP for 19 patients on "inspection", and 36 patients on "inspection and dermoscopy", and 46 patients on "inspection, dermoscopy, and biopsy". Dermoscopy is significantly useful comparing the detection rate (inspection, 0.41; inspection and dermoscopy, 0.78; p = 0.0003; using χ² -test). In addition, we also should learn from the results that the detection rate goes down to 0.78 without a biopsy. Thus, dermoscopy is certainly a useful tool for invisible pustules and also undetectable pustules to detect pustules in PPP. Moreover, we objectively showed that "inspection, dermoscopy, and biopsy" are the best way to make a PPP diagnosis.