Reports of permethrin resistance of Sarcoptes scabiei var. hominis are emerging. We propose that this may be pseudoresistance. The resistance is due to inadequate counselling by physicians, incorrect treatment (insufficient quantity of permethrin; too short length of treatment), and poor adherence and compliance by patients. Other reasons include single application of permethrin, suggestion to apply the drug for 6-8 hours, failed application on subungual folds, irritant contact dermatitis, in particular on genitals, for which some patients stop the treatment, and unexplainable use of permethrin in post-scabies prurigo. Thus, we believe that several cases of resistance to permethrin are actually cases of pseudoresistance.

Pyoderma gangrenosum (PG) is a rare inflammatory skin disease classified within the group of neutrophilic dermatoses. Although its pathophysiology has not been fully elucidated, PG is currently regarded as an autoinflammatory process targeting the pilosebaceous unit in genetically predisposed individuals.¹ Drug-induced PG has been proposed as a model to further our understanding of the disease pathogenesis.²

(1) Background: Onychopapilloma is a benign tumor of the nail bed and distal matrix. which usually manifests as monodactylous longitudinal eryhtronychia associated with subungual hyperkeratosis. The impossibility to rule out a malignant neoplasm is an indication for surgical excision and histological examination. Our aim is to report and describe the ultrasonographic features of onychopapilloma. (2) Methods: we conducted a retrospective analysis of patients with a histological diagnosis of onychopapilloma who underwent ultrasonographic examination in our Dermatology Unit from January 2019 to December 2021. (3) Results: Six patients were enrolled. Erythronychia, melanonychia, and splinter hemorrhages were the main dermoscopical findings. Ultrasonography detected nail bed dishomogeneity in three patients (50%) and a distal hyperechoic mass (5 patients, 83.3%). Color Doppler imaging did not show vascular flow in any of the cases. (4) Conclusions: the detection of a subungual distal non-vascularized hyperechoic mass by US, together with classical onychopapilloma clinical features, supports the diagnosis, especially in those patients who were unable to perform excisional biopsy.