A 48-year-old woman sought care for a widespread pruritic skin eruption that began on her upper back and spread to her arms, lower trunk, and lower legs. She’d had the rash for approximately 2 months and didn’t have any systemic symptoms. A course of prednisone prior to her presentation failed to improve the rash. She denied a personal or family history of rheumatologic or dermatologic disease and reported no new medications or exposures.
On physical exam, she was afebrile and her vital signs were normal. The rash had red-to-salmon–colored scaling patches with discrete and coalescing follicular papules. There were prominent islands of sparing (FIGURE 1).
The patient’s palms were waxy and erythematous and her feet had hyperkeratosis. A complete blood count, comprehensive metabolic panel, and lipid panel were normal. A skin biopsy demonstrated psoriasiform dermatitis with alternating areas of orthokeratosis and parakeratosis (the presence of keratinocyte nuclei within the stratum corneum where nuclei typically aren’t found).