Acute generalized exanthematous pustulosis caused by hydroxychloroquine in a patient with rheumatoid arthritis and CARD14 mutation: Case report

Rationale: Acute generalized exanthematous pustulosis (AGEP) is a serious adverse skin reaction characterized by the rapid appearance of densely distributed, small, sterile pustules with erythema. However, its pathogenesis is not fully understood. Hydroxychloroquine is widely used for the treatment of autoimmune diseases. Some patients presenting with AGEP have IL36RN and CARD14 gene mutations. Our report describes a patient with rheumatoid arthritis and AGEP associated with hydroxychloroquine and a newly discovered CARD14 gene mutation. Patient concerns: A 28-year-old woman with rheumatoid arthritis, treated with leflunomide therapy without marked relief of joint pain, developed multiple rashes with pruritis covering the body 5 days after switching to hydroxychloroquine treatment. Diagnoses: Based on the patient's history, symptoms, and histopathological findings, AGEP was diagnosed. Interventions: Whole-exome sequencing and Sanger validation revealed no mutations in the IL36RN gene; however, a CARD14 gene mutation was present. The patient was treated using ketotifen fumarate tablets, dexamethasone sodium phosphate, calcium gluconate injection, methylprednisolone injection, vitamins C and B12, hydrocortisone butyrate cream, Reed acne cream, potassium chloride tablets, and pantoprazole enteric-coated capsules. Outcomes: The rash improved after 15 days. Lessons subsections: There has been little basic research on AGEP-related genetics, and the CARD14 mutation may underlie several pustular rashes, including AGEP and generalized pustular psoriasis. Follow-up studies and further accumulation of patient data are required.