Crusted Scabies Mimicking Psoriasis in a Patient With Down Syndrome: A Case Report

Crusted scabies, also known as Norwegian scabies, is a rare but highly contagious variant of scabies characterized by extensive hyperkeratotic plaques and a heavy mite burden. It predominantly affects immunocompromised individuals or those with neurological or cognitive impairments, including individuals with Down syndrome. We report the case of a 29-year-old man with Down syndrome who developed a progressive, treatment-resistant erythematosquamous eruption initially misdiagnosed as psoriasis. Topical corticosteroid therapy led to clinical worsening, with widespread hyperkeratotic and crusted plaques. Further evaluation revealed the presence of Sarcoptes scabiei mites and eggs on microscopic examination of skin scrapings. The patient was successfully treated with a combination of oral ivermectin, topical benzyl benzoate, and keratolytic agents, alongside environmental decontamination and the treatment of close contacts. This case underscores the diagnostic challenge of crusted scabies in cognitively impaired patients and highlights the risk of misdiagnosis, particularly as psoriasis, which may delay appropriate treatment and increase the risk of outbreaks. Early recognition, microscopic confirmation, and aggressive multidrug therapy are essential for effective management.