From the Journals

Relapsing scabies? Nails may hold a clue



Nails should not be overlooked in treating common scabies, cautioned Marie Chinazzo, MD, of Centre Hospitalier Régional et Universitaire Tours, France, and her associates.

Nails can harbor mites, representing a potential source for relapse, not only in children, but also in adults.

Scabies on right hand, wrist, and arm wikimedia commons

Few studies have addressed scabies on the nails, which is typically observed in immunocompromised adults with crusted scabies, but also rarely in healthy adults and children.

In an observational, multicenter, prospective study conducted between June 2015 and January 2017, 47 pediatric patients with common scabies, including 3 children under 2 years of age, presented with mites on the first toenail/thumbnail; two of them had already completed treatment and were experiencing relapse. All children with dermatologic diagnosis that was confirmed by visual inspection of “the delta sign” (presence of the mite seen as a triangle representing the head) using dermoscopy or by microscopic identification of Sarcoptes scabiei were included in the study. Dermatologists were required to complete a standardized questionnaire for each participant. Full body inspections and nail samplings also were done.

Clinical nail damage, consisting of hyperkeratosis, onycholysis, onychoschizia, and pachyonychia, appeared in 5 of the 47 patients (11%). No other cause of nail damage was determined in four of the cases, for which mites were not directly visualized, the researchers noted. The report was published in the Journal of Pediatrics.

Of the 47 confirmed cases, 26 were female; 23 were under 2 years of age; 20 were 2-12 years; and 4 were older than 12. Ten cases presented with significant medical history; none were classified as immunocompromised.

Fully 42 of the 47 children (89%) reported pruritus, and of these, 64% also had pruritus present in the family home; 60% of siblings and 45% of parents were affected.

None were diagnosed with crusted scabies. The mean delay from disease onset to diagnosis was 55 days. In 38% of cases, previous treatment for scabies had been rendered.

Treatments varied based on presentation. Ivermectin, esdepallethrin, and 40% urea were repeated after 10 days in at least one case. In another case, an entire family was treated once with topical 5% permethrin; once the child experienced relapse, oral ivermectin was employed. In the case of an 18-month-old girl with pruritus and skin lesions, topical corticosteroid was used for 10 days until such time that dermatoscopy revealed the “delta sign” and 5% topical permethrin was added.

The authors observed that nail scabies in the medical literature is more commonly seen in immunocompromised patients with crusted scabies and higher concentrations of parasites. They were able to locate only three other reports, all in adults, of nail scabies occurring with common scabies.

“Treatment of nail scabies is difficult and is not highly evidence based,” cautioned Dr. Chinazzo and her associates. The primary study limitations were the small patient population and that nail sampling was taken only from the first fingers and toes, which could mean that the number of mites present is actually underestimated, they added.

The authors had no relevant financial disclosures.

SOURCE: Chinazzo M et al. J Pediatr. 2018. doi: 10.1016/j.jpeds.2018.01.038.

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