A case of generalized pustular psoriasis caused by hydroxychloroquine in a patient with systemic lupus erythematosus.

Hydroxychloroquine (HCQ) has been used to treat systemic lupus erythematosus (SLE) in Japan since 2015. We herein report a case of SLE that developed generalized pustular psoriasis (GPP) following the administration of HCQ. Twenty-one days after the HCQ treatment, a pustular rash with itching appeared on the auricle, scalp, and forearm, and spread rapidly to the face and body trunk with a high fever and arthralgia. Skin biopsy showed pustule formation under the cornified layer, neutrophil infiltration, the destruction of keratinocytes, and spongiform pustules of Kogoj. The patient was diagnosed with GPP. HCQ was immediately discontinued, the dose of prednisolone (PSL) was increased, and granulocyte and monocyte adsorption apheresis was performed. Her symptoms subsequently disappeared. Since arthralgia relapsed after the tapering of PSL, cyclosporine was added. Although single nucleotide polymorphisms (c.28C>T and c.115+6T>C) in the interleukin (IL)-36RN gene, which encodes the IL-36 receptor antagonist, have frequently been reported in GPP, these mutations were not observed in the present case. The potential development of GPP needs to be considered when administering HCQ to patients with SLE.