Idiopathic Papular Dermatitis in the Spectrum of Chronic Papular Eruptions (Subacute Prurigo): Reappraisal and Diagnostic Algorithm

Background: The clinical diagnosis of papular eruptions is common but poorly characterized in the literature and the etiology is often unknown. Objective: To characterize the entity of idiopathic papular dermatitis in the spectrum of chronic papular eruptions. Methods: The cohort consisted of patients who presented at a tertiary medical center in 2005–2014 with a papular eruption of at least 4 months’ duration. Findings on histological analysis and thorough clinical investigation, performed in all cases, were collected. The patients completed a questionnaire on disease course and outcome. Results: Sixty-five patients were included. Sixteen patients showed morphological changes over time and were excluded. Investigations in the remaining 49 patients with a consistent papular morphology yielded a well-defined diagnosis in 23 (46%). Twenty-six patients (54%; 14 male) were diagnosed with idiopathic papular dermatitis. Their mean age at onset was 61.6 ± 14.4 years and the mean duration of disease 3.11 ± 2.726 years. In 60%, the rash resolved with conservative treatment during follow-up (mean 4.35 ± 2.53 years). Conclusions: Chronic papular eruptions encompass a wide range of skin diseases. In more than half of the cases, the etiopathogenesis remains unclear. On the basis of our results, we propose a diagnostic algorithm for idiopathic papular dermatitis.

Successful Treatment of Demodex gatoi with 10% Imidacloprid/1% Moxidectin

Demodex gatoi is a transmissible, short-bodied mite found in the stratum corneum of cats. It is known to cause moderate to intense pruritus, often manifested as self-induced alopecia and excoriations. 10% imidacloprid/1% moxidectina is a monthly, topical solution indicated for the treatment and/or prevention of fleas, heartworms, intestinal parasites, and ear mites. A household of cats was presented for pruritus that ranged from mild to severe in 8 of the 13 felines. The most common clinical signs included miliary-type papular dermatitis and focal areas of erythema associated with alopecia. Multiple skin scrapings of each animal revealed Demodex gatoi mites in only two cats. Weekly topical administration of 10% imidacloprid/1% moxidectin was used on all cats in the household for a total of ten doses. Skin scrapings following treatment were negative, and all cats in the house improved. Based on the successful treatment of this small number of cats, weekly application of 10% imidacloprid/1% moxidectin should be considered for the clinical resolution of cats affected by D. gatoi.