Unmasking crusted scabies in Hailey-Hailey disease: a systemic syndrome with musculoskeletal and neuropsychiatric manifestations.

We report a patient with biopsy-proven Hailey-Hailey disease (HHD) in remission who presented with itchy, painful flexural lesions. Initial findings suggested relapse of HHD, but within 72 hours, he developed joint pain, fever, incoherent speech, hallucinations and thick crusted plaques. Skin scrapings confirmed crusted scabies, and he showed irrefutable clinical improvement with oral ivermectin. Our case illustrates the interplay between generalised HHD and crusted scabies, and its rare systemic complications involving the musculoskeletal and neuropsychiatric systems.