A photodistributed rash in a patient on apixaban

A 63-year-old female with recent diagnosis of atrial fibrillation presented with a 1 month history of pruritic rash.Apixaban was started 6 weeks prior to presentation after cardiac ablation.She was using triamcinolone ointment without improvement.Exam showed photodistributed erythematous coalescing scaly papules on the vertex scalp, shoulders, and upper arms, with sharp demarcation along shirt line (Fig 1).Shave biopsy showed interface dermatitis, dermal mucin, and superficial dermal perivascular lymphocytic infiltrate (Figs 2 and3).Lab testing was notable for anti-histone antibody 3.7U (strong positive), elevated liver enzymes, normal complete blood count, and negative anti-nuclear antibody (ANA), anti-SSA, and SSB antibodies.