Postscabies prurigo is an uncommon complication of scabies.
Mechanism: chronic hypersensitivity reaction to scabies mite antigens
Clinical features:
(1) history of scabies that has been successfully treated
(2) red to brown papules and nodules
(3) usual locations: axillae, genitals, groin
(4) severe pruritis
(5) exams (scrapings, dermoscopic, histologic) negative for scabies mites and eggs
(6) no response to topical permethrin and oral ivermectin
The lesions may persist for months if untreated. Treatment may include:
(1) potent topical and intralesional corticosteroids
(2) tacrolimus or pimecrolimus
(3) cryotherapy
Differential diagnosis:
(1) nodular scabies (shows evidence of scabies AND responds to therapy)
