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Crusted scabies mimicking an acrodermatitis continua of Hallopeau.

Background
Crusted scabies (CS) is an uncommon, highly contagious, variant of classic scabies. Elevated concentrations of the mite Sarcoptes scabiei var. hominis are found in the skin lesions, which lead to a more exaggerated clinical picture than in classic scabies. This disease is mainly observed in patients with any kind of immunosuppression and relates to Down syndrome.


Case report
A pediatric female patient with Down syndrome, who presented a crusty white plaque associated with nail dystrophy and subungual hyperkeratosis affecting the distal portion of the fingers is described. Because of these findings, the diagnosis of acrodermatitis continua of Hallopeau was considered. A punch biopsy was performed, attaining the diagnosis of CS. She received systemic treatment with oral ivermectin, topical treatment with emollient cream and desonide 0.1%. Notorious clinical improvement was observed two weeks after finalizing treatment.


Conclusions
CS is variant of scabies prevalent in immunocompromised patients and Down syndrome that can be easily confused with inflammatory pathologies with abnormal epidermal keratinization. This case is considered as an atypical presentation of the disease because of local affection of the fingers and nail dystrophy. The histopathological study was necessary to obtain the diagnosis and rule out differential diagnosis.