Norwegian scabies in immunosuppressed patient misdiagnosed as an adverse drug reaction.

BACKGROUND: Norwegian or crusted scabies is considered a rare affection and presumably represents an abnormal host immune response to Sarcoptes scabiei. As the condition mimics a range of dermatoses, it can be easily misdiagnosed and mismanaged.

CASE REPORT: A 85-year-old woman suffering from bullous pemphigoid was referred for evaluation with presumptive diagnosis of an adverse drug reaction to hydrochlorothiazide or lacipil. Systemic corticosteroid therapy as the mainstay in the control of the bullous skin disorder was increased, but the skin condition worsened. ELISA for the detection of antibodies against the drugs suspected of causing hypersensitivity was negative. Histological examination disclosed inflammatory cells in the upper dermis and parasites. Direct microscopy of the scraped material revealed numerous parasites of the Sarcoptes scabiei type. The patient was treated with topical keratolytics following traditional scabicides for twice as long in comparison with the standard protocol.

CONCLUSION: Norwegian scabies may be misdiagnosed and mismanaged in immunosuppressed patients. The diagnosis of scabies should always be considered in immunosuppressed patients with pruritus.