A Case of Punctate Psoriasis Following Treatment with Cetuximab in a Patient with Metastatic Gastric Adenocarcinoma.

BACKGROUND: In contemporary times, malignancies characterized by metastatic growth have been subjected to innovative therapeutic approaches involving immunological agents known as Programmed Death Receptor 1 (PD-1) inhibitors. Notwithstanding their remarkable immunotherapeutic effectiveness, these treatments can give rise to undesirable immune-related effects. Sintilimab, a PD-1 inhibitor sanctioned for marketing by the Chinese National Medical Products Administration in 2018, has been associated with 51 reported cases of adverse reactions on the market, excluding psoriasis, up to the present moment.

CASE DESCRIPTION: Herein, we report the clinical characteristics of a patient with metastatic gastric adenocarcinoma who developed guttate psoriasis after receiving Sintilimab. The patient was an elderly male presenting with papules varying in size from that of rice grains to soybeans, accompanied by scattered erythematous lesions across his body. Notably, an atypical Auspitz's sign was observed, wherein certain lesions were covered with a minimal amount of scale, coupled with reported persistent itching. The progression of the disease manifested within a span of one week.

CONCLUSION: PD1 inhibitors have been associated with the recurrence, exacerbation, or new onset of psoriasis. Consequently, a personal or family history of psoriasis is an essential risk factor that needs to be considered before PD1 inhibitor medication, which helps with the early diagnosis of psoriasis. Early diagnosis of new-onset guttate psoriasis poses challenges. An early consultation with a dermatologist is recommended, and a conclusive diagnosis can be obtained through a histopathologic examination.